Multiple layer disk reproducing apparatus, and apparatus for reproducing information record medium

ABSTRACT

An apparatus for reproducing a multiple layer disk, which comprising a plurality of layers each having an information record surface on which record information is recorded, is provided with: a read device for reading the record information from each of the layers; a reproduction process device for applying a predetermined reproduction process to the record information read by the read device in accordance with a reproduction process parameter, which is set therein and which comprises at least one of a gain value and an equalizer value, to thereby output a reproduction information signal; a drive device for driving the read device to jump from one reading state for reading one of the layers to another reading state for reading another of the layers; a memory for storing a plurality of reproduction process parameters corresponding to the layers in advance of reproduction; and a set device for reading out one of the stored reproduction process parameters, corresponding to another of the layers as a destination of jumping of the read device, from the memory and setting the read out reproduction process parameter in the reproduction process device, in case that the read device is driven to jump by the drive device.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a division of U.S. patent application Ser. No. 08/855,369 filedon May 13, 1997, now U.S. Pat. No. 6,240,054.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is related with an apparatus for reproducinginformation of an information record medium such as an optical disk, onwhich the information is recorded magnetically or by means of a phasepit and the like, and in which an information record layer is formed inmultiple layers or a one-layer. The present invention is also relatedwith an apparatus for automatically setting, in the reproducingapparatus for reproducing the multiple-layer disk, each loop gain valueand/or equalizer value in a focus servo and a tracking servo, and alevel value and/or an equalizer value in an RF (Radio Frequency) signal,which are optimal for each layer.

2. Description of the Related Art

Recently, DVD (Digital Video or Versatile Disk) has been remarkablydeveloped which dramatically improves a memory density over aconventional CD and services as a high density record medium that canrecord one movie and the like.

Although this DVD has a different disk substrate thickness from the CD,the principle of reading a record pit responsible for storinginformation is similar to that of the CD. Thus, a CD/DVD compatible typeof a reproducing apparatus may be proposed. In this CD/DVD compatibletype of the reproducing apparatus, in order to optimally collect aninformation recording beam on an information record surface of eachdisk, it is considered to employ a bifocal lens that can emit two lightbeams focused on different positions on one straight line, or a methodof exchanging lenses so as to change a focal length in correspondingwith the type of the disk, or other methods.

Incidentally, in the DVD, it is prescribed that a linear velocitythereof is higher than that of the CD from a request of making a densityhigher. So, it is necessary that servo gains and servo frequency bandsin focus and tracking servo circuits are made different between the CDand the DVD. More actually, the DVD is set to be wider in servo band ona high frequency side than the CD. The DVD is set to be larger in servogain than the CD.

Therefore, in order to share the servo circuit between the CD and theDVD in the CD/DVD compatible type of the reproducing apparatus, it isnecessary to adjust the servo gain and the servo band based on the disk.Namely, prior to a reproduction operation, it is judged whether or notan optical disk to be reproduced is the CD or the DVD. The servo gainand the servo band for the disk are correctly adjusted on the basis of asignal indicative of a reflectance factor of the optical disk based onthe judged result, for example, the S-shaped signal of the focus error,an RF signal or the like. The once adjusted value is maintained untilthe disk is exchanged.

There are a single layer disk, where an information record surface onwhich a pit responsible for recording the information is recorded iscomposed of a single layer, and a multiple-layer disk having a pluralityof record layers (for example, two layers) within a same thicknessportion, in the DVD. In a case of the multiple-layer disk, there is, forexample, such a problem that if a gain set for a record layer of a firstlayer in a two-layer disk is used for a record layer in a second layeras it is, the optimization is not performed at the record layer in thesecond layer, because of a relative slope between the respective recordlayers, different reflectance factors of the respective record layers,and other reasons. To solve this problem, it is enough to perform asetting operation of the gain on the basis of the focus error signal andthe like so as to set to a gain corresponding to the record layer at thejump destination, each time the reading beam is jumped from the recordlayer in the first layer to the record layer in the second layer duringreproducing or from the record layer in the second layer to the recordlayer in the first layer. However, in this case, initial setting for thegain and the band should be carried out each time the jump operationbetween the layers is performed. This results in a problem that the jumpoperation takes a long time to complete. Therefore, in a case ofrecording a series of related information, such as movies or the like,over two layers, the jump operation between the layers causes acontinuous reproduction to be interrupted.

In this manner, there is a first problem in the above mentionedreproducing apparatus.

On the other hand, to reproduce the DVD, an apparatus is used whichcomprises an optical pickup for collecting light beams on a focusposition of an information record layer of the DVD and keeps a distancebetween an object lens of the optical pickup and the information recordlayer constant by using a focus servo control, to stably read theinformation.

Here since an area in which a servo error signal can be detected isnarrow in this focus servo control, a so-called focus search operationis required. In this focus search operation, prior to performing thefocus servo control, a servo loop is made open, the objective lens ismoved by a predetermined amount in a direction vertical to theinformation record layer, and a zero cross of a focus error signal(S-shaped signal) outputted at that time is checked, and thereby theservo loop is made close.

However, in case of the DVD of the multiple-layer disk type, since theinformation record layer is composed of multiple layers so as to recordmuch information, it is required to perform the focus search operationfor each layer, to reproduce such a multiple-layer disk from one sidethereof.

That is, in a case of the multiple-layer disk type of the reproducingapparatus, it is necessary to jump the objective lens of the opticalpickup to an appropriate position, each time the information recordlayer to be reproduced is switched. However, since intervals between therespective information record layers are different from each other inthe respective disks within a disk standard, it is not possible tounconditionally set the jump amount. Thus, a standard position for thefocus servo must be set by performing the focus search operation foreach disk and each layer.

Therefore, in a case of the conventional apparatus for performing thefocus search operation, it is necessary to detect the zero cross of thefocus error signal each time the information record layers are switched.As a result, it is difficult to quickly switch between the informationrecord layers in the multiple-layer DVD.

In this manner, there is a second problem in the above mentionedreproducing apparatus.

SUMMARY OF THE INVENTION

It is therefore a first object of the present invention, from theviewpoint of the above mentioned first problem, to provide amultiple-layer disk reproducing apparatus, which can quickly perform astable servo control, even if the reading beam is jumped between thelayers, at a time of reproducing the record information from themultiple-layer disk.

It is therefore a second object of the present invention, from theviewpoint of the above mentioned second problem, to provided anapparatus for reproducing the DVD or the like, which can perform a quickreproducing operation at a time of switching the record layers of theDVD or the like, in which the information record layers may be formed inmultiple layers.

The above mentioned first object of the present invention can beachieved by a first apparatus for reproducing a multiple layer diskcomprising a plurality of layers each having an information recordsurface on which record information is recorded. The first apparatus isprovided with: a read device for reading the record information fromeach of the layers; a reproduction process device for applying apredetermined reproduction process to the record information read by theread device in accordance with a reproduction process parameter, whichis set therein and which comprises at least one of a gain value and anequalizer value, to thereby output a reproduction information signal; adrive device for driving the read device to jump from one reading statefor reading one of the layers to another reading state for readinganother of the layers; a memory for storing a plurality of reproductionprocess parameters corresponding to the layers in advance ofreproduction; and a set device for reading out one of the storedreproduction process parameters, corresponding to another of the layersas a destination of jumping of the read device, from the memory andsetting the read out reproduction process parameter in the reproductionprocess device, in case that the read device is driven to jump by thedrive device.

According to the first apparatus of the present invention, a pluralityof reproduction process parameters corresponding to the layers arestored in the memory in advance of reproduction. In reproduction, therecord information is read from each of the layers, by the read devicesuch as an optical pickup. Then, a predetermined reproduction process isapplied to the record information in accordance with a reproductionprocess parameter, which is set therein and which comprises at least oneof a gain value and an equalizer value, by the reproduction processdevice, such as an RF amplifier, a low pass filter, an A/D converter, afocus gain controller, a digital equalizer and the like. Thus, thereproduction information signal is outputted from the reproductionprocess device. In case that the read device is driven by the drivedevice to jump from one reading state for reading one of the layers toanother reading state for reading another of the layers, one of thestored reproduction process parameters, corresponding to this another ofthe layers as a destination of jumping of the read device, is read outfrom the memory, by the set device. Further, this read out reproductionprocess parameter is set in the reproduction process device, by the setdevice. Accordingly, after jumping, the predetermined reproductionprocess is applied to the record information appropriately in accordancewith the reproduction process parameter, which readily corresponds tothe layer at the jump destination. Therefore, it is not necessary tomeasure or determine the gain value and/or the equalizer value for thelayer at the jump destination each time the jump is performed. Thus, astable and quick servo control can be performed, even if the jumpingoperation between the layers is performed, according to the firstapparatus of the present invention.

In one aspect of the first apparatus of the present invention, thememory stores the reproduction process parameters each comprising atleast one of the gain value of a focus servo loop for the reproductionprocess device and the gain value of a tracking servo loop for thereproduction process device.

According to this aspect, since the gain value of the focus servo loopand/or the gain value of the tracking servo loop are stored in thememory, the stability of each servo loop in reproduction can beimproved, so that the servo control operation can be quickly and stablyperformed.

The above mentioned first object of the present invention can be alsoachieved by a second apparatus for reproducing a multiple layer diskcomprising a plurality of layers each having an information recordsurface on which record information is recorded. The second apparatus isprovided with: a read device having an objective lens for opticallyreading the record information from each of the layers through theobjective lens a reproduction process device for applying apredetermined reproduction process to the record information read by theread device in accordance with at least one of a gain value and anequalizer value of a focus servo loop, and a gain value and an equalizervalue of another servo loop other than the focus servo loop, which areset therein, to thereby output a reproduction information signal and afocus error signal corresponding to the reproduction information signal;a drive device for driving the read device to move the objective lens ina focus direction of the objective lens; a first measurement device formeasuring at least one of the gain value and the equalizer value of thefocus servo loop for each of the layers on the basis of the focus errorsignal of each of the layers; a second measurement device for measuringat least one of the gain value and the equalizer value of another servoloop for one of the layers on the basis of a reflectance factor of oneof the layers; a memory for storing the measured gain values andequalizer values measured by the first and second measurement devices; acalculation device for calculating a ratio of at least one of the gainvalue and the equalizer value of the focus servo loop for one of thelayers with respect to those for another of the layers; and a set devicefor setting the gain value and the equalizer value of another servo loopfor another of the layers on the basis of the ratio calculated by thecalculation device, to the reproduction process device.

According to the second apparatus of the present invention, inreproduction, the record information is optically read from each of thelayers through the objective lens, by the read device. Then, apredetermined reproduction process is applied to this record informationin accordance with at least one of a gain value and an equalizer valueof a focus servo loop and a gain value and an equalizer value of anotherservo loop other than the focus servo loop (e.g., a tracking servo loop,a spindle servo loop), which are set therein, by the reproductionprocess device. Thus, a reproduction information signal and a focuserror signal corresponding to the reproduction information signal areoutputted by the reproduction process device. In case that the readdevice is driven to move the objective lens in a focus direction of theobjective lens between the layers, by the drive device, at least one ofthe gain value and the equalizer value of the focus servo loop for eachof the layers is measured on the basis of the focus error signal of eachof the layers, by the first measurement device. Further, at least one ofthe gain value and the equalizer value of another servo loop (e.g., atracking servo loop, a spindle servo loop) for one of the layers ismeasured on the basis of a reflectance factor of this one of the layers,by the second measurement device. Then, these measured gain values andequalizer values are stored in the memory. Then, a ratio of the gainvalue and/or the equalizer value of the focus servo loop for this one ofthe layers with respect to those for another of the layers is calculatedby the calculation device. Finally, the gain value and the equalizervalue of another servo loop (e.g. a tracking servo loop, a spindle servoloop) for another of the layers is set on the basis of the calculatedratio to the reproduction process device, by the set device.Accordingly, before or after moving the objective lens in the focusdirection, the predetermined reproduction process is applied to therecord information appropriately in accordance with the gain valueand/or the equalizer value, which readily corresponds to the layerbefore or after the movement of the objective lens. Since the gain valueand/or the equalizer value of the servo loop for the layer or layersother than one layer is obtained by use of the ratio, the stability ofeach servo loop in reproduction can be improved while the servo controloperation can be more stably and quickly performed, according to thesecond apparatus of the present invention.

In one aspect of the second apparatus of the present invention, thefirst measurement device takes in focus error signals of all the layersfrom the reproduction process device while the objective lens is movedup or down just once, to thereby measure at least one of the gain valueand the equalizer value of the focus servo loop for each of the layers.

According to this aspect, the focus error signals of all the layers aretaken in while the objective lens is moved up or down just once. Thus,the servo control operation can be even more stably and quicklyperformed.

On the other hand, in another aspect of the first apparatus of thepresent invention, the first apparatus is further provided with adetection device for detecting a maximum amplitude value of an RF signalof each of the layers, from the record information read by the readdevice. The memory stores at least one of the gain value and theequalizer value for the RF signal, which are obtained from the maximumamplitude value detected by the detection device.

According to this aspect, a maximum amplitude value of an RF signal ofeach of the layers, is detected from the record information read, by thedetection device. Then, at least one of the gain value and the equalizervalue for the RF signal, which are obtained from the maximum amplitudevalue detected by the detection device, are stored in the memory.Therefore, it is possible to reproduce the RF signal accurately inreproduction.

The above mentioned first object of the present invention can be alsoachieved by a third apparatus for reproducing a multiple layer diskcomprising a plurality of layers each having an information recordsurface on which record information is recorded. The third apparatus isprovided with: a read device for reading the record information fromeach of the layers; a detection device for detecting a maximum amplitudevalue of an RF signal of each of the layers, from the record informationread by the read device; a reproduction process device for applying apredetermined reproduction process to the record information read by theread device in accordance with a reproduction process parameter, whichis set therein and which comprises at least one of a gain value and anequalizer value, to thereby output a reproduction information signal; amemory for storing a plurality of predetermined reproduction processparameters in advance of reproduction; and a selection device forselecting one of the predetermined reproduction process parametersstored in the memory, on the basis of the maximum amplitude valuedetected by the detection device, and setting the selected reproductionprocess parameter in the reproduction process device.

According to the third apparatus of the present invention, a pluralityof predetermined reproduction process parameters are stored in thememory in advance of reproduction. In reproduction, the recordinformation is read from each of the layers, by the read device. Then, amaximum amplitude value of an RF signal of each of the layers isdetected from the record information read, by the detection device.Then, a predetermined reproduction process is applied to this recordinformation in accordance with a reproduction process parameter, whichis set therein and which comprises at least one of a gain value and anequalizer value, by the reproduction process device. Thus, areproduction information signal is outputted by the reproduction processdevice. At this time, if the layer to be reproduced is changed, one ofthe predetermined reproduction process parameters stored in the memoryis selected on the basis of the detected maximum amplitude value, by theselection device. And that, the selected reproduction process parameteris set in the reproduction process device. Therefore, since the gainvalue and/or the equalizer value can be selected from the memory inaccordance with the maximum amplitude value, the servo control operationfor the RF signal can be reproduced quickly by use of the gain valueand/or the equalizer value, which readily corresponds to the pertinentlayer without the necessity of measuring and/or calculating the gainvalue and/or the equalizer value of the RF signal for the pertinentlayer, according to the third apparatus of the present invention.

The above mentioned second object of the present invention can beachieved by a fourth apparatus for reproducing an information recordmedium comprising one or a plurality of layers each having aninformation record surface on which record information is recorded. Thefourth apparatus is provided with: a read device having an objectivelens for optically reading the record information from the informationrecord surface through the objective lens; a reproduction process devicefor applying a predetermined reproduction process to the recordinformation read by the read device, to thereby generate a reproductioninformation signal and a focus error signal corresponding to thereproduction information signal; a drive device for driving the readdevice to move the objective lens in a focusing direction of theobjective lens according to a control signal; a time counting device formeasuring a time interval between two successive focus error signalsgenerated by the reproduction process device; an interval calculationdevice for calculating a layer interval between the layers on the basisof the time interval measured by the time counting device if a pluralityof focus error signals are generated, which have signal levels exceedinga predetermined standard value set in advance, while the objective lensis moved in either one direction by the drive device; a selection devicefor selecting one parameter for the control signal, which corresponds tothe layer interval calculated by the interval calculation device, amonga plurality of parameters for the control signal, which are set inadvance to move the objective lens between the layers; a parametermemory for storing the parameter selected by the selection device; and acontrol device for generating the control signal based on the parameterstored in the parameter memory, and thereby controlling the drive deviceto drive the read device to move the objective lens.

According to the fourth apparatus of the present invention, inreproduction, the record information is read from the information recordsurface through the objective lens, by the read device. Then, apredetermined reproduction process is applied to this recordinformation, by the reproduction process device. Thus, a reproductioninformation signal and a focus error signal corresponding to thereproduction information signal are generated by the reproductionprocess device. In the operation of the fourth apparatus especially, atime interval between two successive focus error signals generated bythe reproduction process device is measured by the time counting device.In this condition, if the read device is driven by the drive device tomove the objective lens in the focusing direction according to thecontrol signal i.e., if the objective lens is moved toward or away fromthe information record medium, the focal point of the objective lenspasses through the information record surface of the layer or layers ofthe information record medium. Thus, the focus error signal is generatedin correspondence with the passed information record surface. While theobjective lens is moved in either one direction by the drive device inthis manner, if a plurality of focus error signals are generated, whichhave signal levels exceeding a predetermined standard value set inadvance, the layer interval (i. e. a distance between the informationrecord surfaces of two adjacent layers) is calculated on the basis ofthe time interval measured by the time counting device, by the intervalcalculation device. Namely, such a fact that a plurality of focus errorsignals, which have signal levels exceeding the predetermined standardvalue, are generated during the movement of the objective lens in onedirection in this way, indicates that the pertinent information recordmedium is a multiple layer type. Thus, the layer interval of theinformation record medium can be obtained by the relationship betweenthe moving speed of the objective lens, which is a predetermined value,and the measured time interval. After the layer interval is calculatedin this manner, one parameter for the control signal, which correspondsto the calculated layer interval, is selected among a plurality ofparameters for the control signal, which are set in advance to move theobjective lens between the layers, by the selection device. Then, thisselected parameter is stored in the parameter memory. After that, thecontrol signal is generated on the basis of the parameter stored in theparameter memory, by the control device, and that the drive device iscontrolled according to this generated control signal. Therefore, aslong as a reproduction operation is performed with respect to anydesirable layer of the pertinent information record medium, byoutputting the control signal based on the stored parameter in theparameter memory, the objective lens can be moved to an appropriateposition with respect to this desirable layer.

In this manner, it is possible to move the objective lens quickly andaccurately so as to position its focal point on the information recordsurface of any desirable layer of the information record medium even ifthe information record medium comprises one layer or a plurality oflayers, so that the reproduction of such an information record mediumcan be smoothly performed.

In one aspect of the fourth apparatus of the present invention, thedrive device drives the read device to move the objective lens when apulse signal is applied as the control signal to the drive device. Theparameter for the control signal comprises at least one of a pulsewidth, a peak value, a brake time and a gain up time of the pulsesignal.

According to this aspect, the objective lens is moved when the pulsesignal is applied to the drive device. At this time, the moving distanceand the stability of the movement of the objective lens depends upon thepulse width, the peak value, the brake time and the gain up time of thepulse signal. Therefore, by storing at least one of these parameters andby outputting the control signal based on these stored parameters to thedrive device, it is possible to move the objective lens by a desirablemoving distance i.e., to move the objective lens quickly and accuratelyso as to position its focal point on the information record surface ofany desirable layer of the pertinent information record medium, so thatthe reproduction of such an information record medium can be smoothlyperformed.

In another aspect of the fourth apparatus of the present invention, thefourth apparatus is further provided with a discrimination device fordiscriminating a type of the information record medium on the basis ofthe time interval measured by the time counting device, as for the focuserror signal, which is generated during a reciprocation motion of theobjective lens by the drive device and which exceeds the predeterminedstandard value.

According to this aspect, if the objective lens is moved toward theinformation record medium, for example, the time interval from the timepoint of staring the movement until the focus error signal exceeding thestandard value is generated, becomes shorter as the distance from thesurface of the information record medium to the information recordsurface corresponding to the focus error signal becomes shorter, andbecomes longer as this distance becomes longer. Further, in case of theinformation record medium of the multiple layer type, a plurality ofsuccessive focus error signals are generated. On the other hand, afterthe objective lens arrives at its upper limit position, if the objectivelens is nextly moved away from the information record medium, forexample, the time interval from a time point of starting this movementuntil the focus error signal firstly exceeding the standard levelbecomes shorter as the distance from the surface to the informationrecord surface of the information record medium becomes longer, andbecomes longer as this distance becomes shorter. Further, in case of theinformation record medium of the multiple layer type, a plurality ofsuccessive focus error signals are generated. Therefore, if theobjective lens is moved in this way, the time interval between twosuccessive focus error signals becomes shorter as the distance from thesurface to the information record surface becomes longer, becomes longeras this distance becomes shorter, and becomes the shortest in case ofthe multiple layer type. On the other hand, if the moving order of theobjective lens is inverted, an inverse relationship between the timeinterval and the distance of the above is obtained. In this manner, thetype of the information record medium is discriminated by thediscrimination device on the basis of the time interval measured by thetime counting device, as for the focus error signal, which is generatedduring a reciprocation motion of the objective lens and which exceedsthe predetermined standard value. Furthermore, if the type of theinformation record medium is discriminated as the multiple layer type,the calculation of the layer interval as well as the selection andstorage of the parameter for the control signal based on the calculationresult are performed.

Consequently, the movement of the objective lens for the desirable layerof the information record medium can be quickly and accuratelyperformed, and, even in case of the information record medium of themultiple layer type, the reproduction can be smoothly performed. Incorrespondence with the type of the information record medium, the focusservo control can be performed accurately.

In another aspect of the fourth apparatus of the present invention, thereproduction process device further generates a tracking error signalcorresponding to the reproduction information signal. And that, thefourth apparatus is further provided with: a servo calculation devicefor calculating at least one of a focus gain value and a tracking gainvalue of each of the layers on the basis of at least one of the focuserror signal and the tracking error signal generated by the reproductionprocess device; a gain memory for storing at least one of the focus gainvalue and the tracking gain value calculated by the servo calculationdevice; and a servo control device for performing at least one of afocus servo control and a tracking servo control, on the basis of atleast one of the focus gain value and the tracking gain value stored inthe gain memory.

According to this aspect, in reproduction, a tracking error signal isfurther generated by the reproduction process device. Then, at least oneof a focus gain value and a tracking gain value of each of the layers iscalculated by the servo calculation device on the basis of at least oneof the focus error signal and the tracking error signal. For example,the peak to peak values of the focus error signals are taken in and theaverage of these values is calculated, so that the focus gain value iscalculated and stored into the gain memory, while the peak to peakvalues of the tracking error signals are taken in and the average ofthese values is calculated, so that the tracking gain value iscalculated and stored into the gain memory. In this operation, at thetime of taking in the focus error signals, the calculation of the layerinterval as well as the selection and storage of the parameter for thecontrol signal is performed. Therefore, in case of reproducing theinformation record medium of the multiple layer type, the movement ofthe objective lens for the desirable layer can be performed on the basisof the parameter stored in the parameter memory, and the focus servocontrol and/or the tracking servo control can be performed on the basisof the focus gain value and/or the tracking gain value stored in thegain memory.

Consequently, the reproduction of the information record medium, whichmay be the single layer type or the multiple layer type, can beperformed even more smoothly.

The nature, utility, and further features of this invention will be moreclearly apparent from the following detailed description with respect topreferred embodiments of the invention when read in conjunction with theaccompanying drawings briefly described below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a multiple layer disk reproducing apparatusas a first embodiment of the present invention;

FIG. 1A is one diagram showing a wave form of a focus error generated byan optical pickup of bifocal lens type in a CD/DVD compatiblereproducing apparatus for use in the embodiment;

FIG. 1B is another diagram showing the wave form of the focus errorgenerated by the optical pickup of bifocal lens type in the CD/DVDcompatible reproducing apparatus for use in the embodiment;

FIG. 2A is a cross-sectional view of a DVD of a multiple layer disk typeto be reproduced in the first embodiment;

FIG. 2B is a diagram showing a relationship between a structure of abifocal lens and a focus error signal in the embodiment;

FIG. 3A is one time chart of a generation of a focus error signal of afirst layer in the first embodiment;

FIG. 3B is another time chart of the generation of the focus errorsignal of the first layer in the first embodiment;

FIG. 3C is another time chart of the generation of the focus errorsignal of the first layer in the first embodiment;

FIG. 4A is one time chart of a generation of a focus error signal of asecond layer in the first embodiment;

FIG. 4B is another time chart of the generation of the focus errorsignal of the second layer in the first embodiment:

FIG. 4C is another time chart of the generation of the focus errorsignal of the second layer in the first embodiment;

FIG. 5 is one flow chart showing an operation of the first embodiment;

FIG. 6 is another flow chart, continued from FIG. 5, showing theoperation of the first embodiment;

FIG. 7A is one time chart of a generation of a focus error signal in asecond embodiment of the present invention;

FIG. 7B is another time chart of the generation of the focus errorsignal in the second embodiment;

FIG. 7C is another time chart of the generation of the focus errorsignal in the second embodiment;

FIG. 8 is one flow chart showing an operation of the second embodiment;

FIG. 9 is another flow chart, continued from FIG. 8, showing theoperation of the second embodiment;

FIG. 10 is a flow chart showing an operation of a third embodiment ofthe present invention;

FIG. 11 is a flow chart showing an operation of a method ofdiscriminating the disk in lens exchanging type for use in theembodiments;

FIG. 12 is a flow chart showing an operation of a method ofdiscriminating the disk in bifocal lens type for use in the embodiments;

FIG. 13 is a flow chart showing an operation of a fourth embodiment ofthe present invention;

FIG. 14 is a flow chart showing an operation of a fifth embodiment ofthe present invention;

FIG. 15 is a flow chart showing an operation of a sixth embodiment ofthe present invention;

FIG. 16 is a block diagram showing a summarized construction of areproducing apparatus for an information record medium as a seventhembodiment of the present invention;

FIG. 17 is a timing chart showing one example of control signals etc.with respect to a focus driver in the seventh embodiment;

FIG. 18 is a timing chart showing another example of control signalsetc. with respect to the focus driver in the seventh embodiment;

FIG. 19 is a timing chart showing a moving condition of an objectivelens of an optical pickup, a focus error signal obtained thereat and astart and stop operation of a timer in the seventh embodiment;

FIG. 20A is a timing chart showing one example of a time-measurementtiming for intervals of the focus error signals in the seventhembodiment;

FIG. 20B is a timing chart showing another example of a time-measurementtiming for intervals of the focus error signals in the seventhembodiment;

FIG. 21 is a flow chart showing an operation of controlling a layerinterval measurement in the seventh embodiment;

FIG. 22 is a flow chart showing an operation of controlling a layerinterval measurement in an eighth embodiment of the present invention;

FIG. 23 is a timing chart showing a moving condition of an objectivelens of an optical pickup, a focus error signal obtained thereat and astart and stop operation of a timer in the eighth embodiment;

FIG. 24 is a block diagram showing a summarized construction of areproducing apparatus for an information record medium as a ninthembodiment of the present invention;

FIG. 25 is one flow chart showing an operation of controlling a layerinterval measurement in the ninth embodiment;

FIG. 26 is another flowchart, continued from FIG. 25, showing theoperation of controlling the layer interval measurement in the ninthembodiment;

FIG. 27 is a flowchart showing an operation of discriminating a disk inthe ninth embodiment;

FIG. 28A is a timing chart showing a moving condition of an objectivelens of an optical pickup, a focus error signal obtained thereat and astart and stop operation of a timer in the ninth embodiment;

FIG. 28B is one timing chart of balance control and tracking gaincontrol operations in the ninth embodiment; and

FIG. 28C is another timing chart of balance control and tracking gaincontrol operations in the ninth embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[I] Construction of Reproducing Apparatus

FIG. 1 shows a block diagram of a multiple-layer disk reproducingapparatus of an embodiment according to the present invention. Anoptical disk 20 to be reproduced is rotated at a defined rotation numberby a spindle motor 21. An optical pickup 22 employing a bifocal lensreads out information, by means of alight beam, from a pit formed on aninformation record surface of the optical disk 20. An output signal fromthe optical pickup 22 is inputted to an RF Amp 23, and is outputted asan analog signal, such as a focus error signal, a tracking error signalor the like. A focus error signal outputted by the RF Amp 23 is sent toa variable amplifier 25, after unnecessary frequency components areremoved through an LPF (Low Pass Filter) 24. A gain of this variableamplifier 25 is set by a command from an FGA (Focus GAin controller) 27described later. An output signal from the variable amplifier 25 isconverted from an analog signal into a digital signal by an A/Dconverter 26, and is then sent to the FGA 27.

An output from the FGA 27 is weighted into particular frequency rangesby a D·EQ (Digital Equalizer) 28, is pulse-width-converted by a PWM(Pulse Width Modulator) 29, and is then supplied to a focus coil (notshown) of the optical pickup 22 by a focus coil drive circuit 30. ThisPWM 29 is a circuit of sending a signal to the focus coil drive circuit30. However, a command from a servo controller 38 described later canprevent the PWM 29 from sending the signal to the focus coil drivecircuit 30. Thus, the PWM 29 also has a role as a focus loop switch usedto make a focus loop in an open path state or a close path state.

On the other hand, the tracking error signal outputted by the RF Amp 23is supplied to a variable amplifier 32, after unnecessary frequencycomponents are removed through an LPF 31. An output signal from thevariable amplifier 32 is converted from an analog signal into a digitalsignal by an A/D converter 33, and then supplied to a TGA (Tracking GAincontroller) 34. An output from the TGA 34 is weighted into particularfrequency ranges by a DEQ 35, is pulse-width-converted by a PWM 36, andis then supplied to a tracking coil (not shown) of the optical pickup 22by a tracking drive circuit 37. There is also the servo controller 38for giving commands to the respective circuits on the basis of dataobtained by the FGA 27, the TGA 34, the respective D EQs 28 and 35, andthe like. Calculation of the data is performed, and the command isgiven, as the occasion demands, by the servo controller 38. A ROM 39 anda CPU 40, in which respective defined values required by themultiple-layer disk type of the reproducing apparatus are stored, areconnected to the servo controller 38.

An operation section 41 and a RAM 42 are connected to this CPU 40.Various information detected at an initial operation in themultiple-layer disk type of the reproducing apparatus is stored in theCPU 40, and read therefrom as the occasion demands. A TR·BL (TrackingBaLance control circuit) 43 is connected to the servo controller 38.After a control signal of a tracking balance is converted from a digitalsignal into an analog signal by a D/A converter 44, a signal is suppliedto the RF Amp 23, and the optimal tracking balance is accordinglyperformed. On the other hand, the RF signal obtained by the RF Amp 23 issupplied through an amplifier 45 to an EFM (Eight to FourteenModulation) decoder 46. The spindle motor 21 is driven by a spindlemotor drive circuit 47, and thereby the optical disk 20 is rotated atthe defined rotation speed.

An RF gain that is optimal for each of the layers in the multiple-layerdisk is supplied through an A/D converter 49 to an RGA (RF GAin controlcircuit) 48, by the command from the servo controller 38. Moreover, theamplifier 45 is controlled by the RGA 48 based on the control signalfrom the servo controller 38. The optimal data is supplied to the EFMdecoder 46. Accordingly, the rotation speed of the spindle motor 21 ismonitored and controlled.

One example of a bifocal lens employed by the optical pickup 22 isexplained here in detail with reference to FIGS. 1A and 1B.

As shown in FIG. 1A, a bifocal lens 12 has a configuration in which adiffraction grating 13 and an objective lens 11 are arranged on oneoptical path. Light beams made parallel to each other by a collimatorlens 14 are divided into three beams: a 0 order light and ±1 orderlights, by the diffraction grating 13 (the −1 order light is not shown).Utilization of a difference between the optical path lengths of the 0order light and the +1 order light among them enables the 0 order lightand the +1 order light to be focused on different positions on an onestraight line.

Actually, for the information record surface of the DVD or the CD, the+1 order light is adapted to be focused on a farther position from theobjective lens 11 than the 0 order light. Thus, the 0 order light is setso as to be optimally collected on the information record surface of theDVD, and the +1 order light is set to be optimally collected on theinformation record surface of the CD. In a case of considering that anoptical pickup using this bifocal lens is gradually made close to anoptical disk, the beam of the +1 order light is firstly emitted to theinformation record surface of the optical disk. Then, an S-shaped signalservicing as a focus error signal is outputted from a four-divisionphoto diode built in the optical pickup (not shown) of the diskreproducing apparatus. Next, an S-shaped signal is obtained whichservices as a pseudo focus error signal generated when a reflectionlight from the optical disk of the +1 order light returns through theoptical path of the 0 order light. Finally, an S-shaped signal isobtained which services as a focus error signal corresponding to the 0order light.

FIG. 1B shows the manner in which the S shapes of the 0 order light, thepseudo light and the +1 order light are generated as mentioned above ina case that the bifocal lens is made close to the optical disk.

A light division ratio of the 0 order light to the +1 order light at thediffraction grating 13 is set to be substantially equal to each other.Since the optimal collection of the 0 order light is performed for theDVD and the optimal collection of the +1 order light is performed forthe CD, the optimally collected situation cannot be kept for the reversecombination thereof, for example, because of generation of sphericalaberration and the like. Thus, in a case that the optical disk is theCD, the S-shaped signal of the focus error signal corresponding to the+1 order light has the highest level (FE1), and the S-shaped signal ofthe focus error signal corresponding to the 0 order light has the lowestlevel. In contrast with this condition, in a case that the optical diskis the DVD, the S-shaped signal of the focus error signal correspondingto the 0 order light has the highest level (FE2), and the S-shapedsignal of the focus error signal corresponding to the +1 order light hasthe lowest level.

[II] Explanation of One-Sided Two-Layer Disk

In a case of an optical disk for DVD shown in FIG. 2A, two transparentoptical disk substrates are bonded together. Each of the substrates hasa diameter of, for example, 120 mm and a thickness of, for example, 0.6mm. A protective layer of a first optical disk (A surface) and aprotective layer of a second optical disk (B surface), which areopposite to each other, are bonded together with adhesive, and therebyconstitute the optical disk substrate having a thickness of 1.2 mm.

A pit for recording information on a surface of a transparent substrate9 made of synthetic resin of polymethylene methacrylate andpolycarbonate is concentrically or spirally formed on the A surface. Areflection layer 1 as a first translucent layer, in which a displaypattern, such as a character, a symbol, a picture or the like, isconstituted by a metallic thin film made of aluminum having silver-whitecolor or the like, is formed on some surface of the transparentsubstrate 9 on which this pit is formed.

Moreover, a reflection layer 2 as a second layer composed of a metallicthin film having golden color made of gold and the like is formed on atop surface of the reflection layer 1 as the first layer and a topsurface of the transparent substrate 9 on which the reflection layer 1as the first layer is not formed. A surface where the reflection layer 1as the first layer and the reflection layer 2 as the second layer are incontact with the pit has substantially same reflectance factors. Aprotective layer 3 made of ultraviolet curing resin is formed on a topsurface of the reflection layer 2 as the second layer. That is, the Asurface disk servicing as a first optical disk is an optical disk havingthe two-layer structure composed of the transparent substrate 9, thepit, the reflection layer 1 as the first layer, the reflection layer 2as the second layer, the protective layer 3 and the like. Similarly tothe A surface disk, a pit for recording information on a surface of atransparent substrate 8 is formed on a second optical disk (B surface),and a protective layer 5 is formed on top surfaces of a reflection layer7 as the first layer and a reflection layer 6 as the second layer. Asmentioned above, the optical disk substrate having the thickness of 1.2mm is constituted by making the protective layers 3 and 5 of these twooptical disk substrates opposite to each other and bonding together witha hot melt type adhesive 4.

When reproducing the multiple-layer disk substrate having the abovementioned multiple-layer structure from one side thereof, if reproducingby using a bifocal lens, S-shapes with respect to the first layer andthe second layer are continuously generated for each of the 0 orderlight, the pseudo light and the +1 order light as shown in FIG. 2B, in afocus error signal generated when the lens is moved up and down, sincean interval between the first layer and the second layer is narrow(approximately 40 μm).

[III] First Embodiment of the Invention

In a first embodiment of the present invention, a focus error signal isextracted, which is generated from the first layer, among focus errorsignals generated by applying an UP or DOWN operation to the objectivelens while emitting light beams to the one-sided two-layer disk loadedon a disk loading surface of the reproducing apparatus. A gain value isset for a focus servo on the basis of this focus error signal. Afterthat, a balance adjustment and again value setting are performed for atracking servo on the basis of a tracking error signal. Next, a focusjump is performed to a second layer, and the operation similar to thatof the above mentioned case is performed for the second layer. The abovementioned operation is performed as a setup (initial setting) operationprior to an actual reproduction operation.

An operation of the first embodiment according to the present inventionis explained with reference to operation time charts in FIGS. 3 and 4and flow charts of FIGS. 5 and 6. At first, FIG. 3A shows two focuserror signals (hereafter, referred to as FE) detected by the opticalpickup 22 when the lens is moved up and down (in a case of two layers).FIGS. 3A to 3C show only an S shape of the FE original to the disk,among the +1 order light, the pseudo light and the 0 order light. Thatis, only the S shape of the FE generated by the 0 order light is shownin this embodiment. In FIG. 3A, a symbol N indicates a number at whichthe lens is moved up and down. As shown in FIG. 3B, T1 is a timerequired from a time point when an amplitude voltage of FE1 firstlygenerated since the up action of the lens exceeds a defined threshold(referred to as TH) stored in the ROM 39 of the multiple layer disk typeof the reproducing apparatus, until a time point when the lens is movedup to the maximum set position.

T2 is a time required from a time point when an amplitude voltage of FE2firstly generated since the down action of the lens exceeds thethreshold TH, until a time point corresponding to an end of the S-shapedcharacteristics of the FE2. T3 is a time required from a time point whenan amplitude voltage of a second FE1 exceeds the threshold TH, until atime point when the lens is moved down to a set end position in the downaction of the lens. In FIG. 3C, T4 is a time required for a trackingbalance adjustment to be firstly performed described later. T5 is a timerequired for a tracking gain adjustment to be firstly performed.

FIGS. 4A to 4C show operation time charts in a case that the opticalpickup 22 is moved to a second layer, similarly to the case of FIGS. 3Ato 3C. T6 is a time required from a time point when the amplitudevoltage of the FE1 firstly generated since the up action of the lensexceeds the defined TH stored in the ROM 39 of the multiple-layer disktype of the reproducing apparatus, until a time point corresponding toan end of the S-shaped characteristics of the FE1.

T7 is a time required from a time point when an amplitude voltage of asecond focus error signal FE2 exceeds the threshold TH, until a timepoint when the lens is moved up to the maximum set position. T8 is atime required from a time point when the amplitude voltage firstlygenerated since the down action of the lens exceeds the threshold TH,until a time point when the lens is moved down to the set end point inthe down action of the lens. In FIG. 4C, T9 is a time required for atracking balance adjustment to be performed for the second layer. T10 isa time required for a tracking gain adjustment to be performed for thesecond layer.

The operation of the first embodiment according to the present inventionis explained with reference to flow charts shown in FIGS. 5 and 6. Atfirst, it is judged at a step S1 whether or not the optical disk is set.If the optical disk is set, various data set when previously reproducingthe optical disk is initialized at a step S2. That is, values ofcounters and timers (which are not shown) are reset which areincorporated within the multiple-layer disk type of the reproducingapparatus used from now.

A disk discrimination of various disks is performed at a step S3. Theoperation of the disk discrimination is explained with reference toflowcharts in FIGS. 12 and 13 described later in detail. The lens ismoved down to a defined position at a step S4. A number that the lens isrepeated to be moved up and down is counted at a step S5. Each time thelens is moved up or down, one is added to the number. A value of N atthat time is stored in an RAM 42. The lens is moved up at a definedspeed at a step S6. A defined threshold (referred to as TH), which isstored in advance in the ROM 39 of the multiple-layer disk type of thereproducing apparatus, is compared with the obtained FE value at thestep S6. In a case that the FE value is not obtained (step S7: NO), theoperation flow returns to the step S6. The lens is continued to be movedup at the defined speed. If the obtained FE1 complies with FE1≧TH (stepS7: YES), the operation flow proceeds to a step S8. The timer starts acounting operation for the time T1.

Next, the maximum amplitude value FEp-p of the FE1 at N=a first time istaken in at a step S9, and stored in the RAM 42. At a step S10, it isjudged whether or not the counted time by the timer exceeds the definedtime T1. If it is judged that the counted time does not exceed thedefined time T1 (Step S10: NO), the lens is continued to be moved upuntil the counted time by the timer reaches the defined time T1. If itreaches the defined time T1 (Step S10; YES), the operation flow proceedsto a step S11, one is added to the N, and further the lens is moved downat a step S12. Next, the operation flow proceeds to a step S13. and itis judged whether or not the FE value in the second layer obtained whenthe lens is moved down is equal to or more than the threshold TH. If theFE value is equal to or less than the threshold TH (Step S13: NO), thisindicates that the FE resulting from the 0 order light is not obtainedyet in the output of the RF Amp 23. Thus, the operation flow returns tothe step S12, and the lens is continued to be moved down. If the FEvalue exceeds the threshold TH (Step S13: YES), the operation flowproceeds to a step S14, and this causes the timer to start the countingoperation for the defined time T2.

In a case where it is judged at a step S15 that the counted time T bythe timer reaches the defined time T2 (step S12: YES), the operationflow proceeds to a step S16, and the FE value equal to or more than thethreshold TH is detected. The FE value detected at this step indicatesthe FE1 of the first layer when the lens is moved down. At a time pointwhen an amplitude value of the FE1 crosses the TH level, this causes thetimer to start the counting time for the defined time T3 (Step S17).Next, the maximum amplitude value FEp-p of the FE1 at N=a second time istaken in at a step S18, and stored in the RAM 42. Then, at a step S19,it is judged whether or not the counted time T by the timer exceeds thedefined time T3. If it exceeds the defined time T3 (step S19: YES), theoperation flow proceeds to a step S20, and the number N that the lens ismoved up and down is monitored. If the number N is less than 4 (StepS20: NO), the operation flow returns to the step S5, and then themaximum amplitude value of the FE1 associated with the up and downaction of the lens is continued to be taken in.

On the other hand, if the number N exceeds 4 (Step S20: YES), theoperation flow proceeds to a step S21, and the focus gain is adjustedfor the first layer. At this time, the adjusted gain value is determinedby the maximum amplitude value of the FE1, in the up and down action ofthe lens, which is stored in the RAM 42 at the steps S9 and S18. Forexample, in a case that the up and down action of the lens is performedfour times, the maximum amplitude values of the FE1s of the four samplesare stored in the RAM 42. Thus, an average value of these maximumamplitude values of the four samples is calculated, and then the servogain is set such that this average value becomes a predeterminedamplitude value. Incidentally, the example in which the number of the upand down actions of the lens is 4 is explained in this embodiment.However, it is not limited to this number. So, it is possible toproperly change the number as the occasion demands.

Next, after the lens is moved up to a position at which the FE1 in thefirst layer is adjacent to a zero-cross point (Step S22), a servo closesignal is outputted by the servo controller 38. The PWM 29 generates apulse signal for driving a focus coil on the basis of the output signalfrom the FGA 27, that is, the focus error signal, corresponding to theservo close signal outputted by the servo controller 38. In this way,since the PWM 29 becomes active, a focus servo loop is made close (StepS23). Then, the operation flow proceeds to a step S24, and this causesthe timer to start the counting time for the defined time T4. Next, inorder to detect a center level (TRCL) of the tracking error (TE) signal,for example, the maximum peak value and the minimum peak value of the TEsignal are taken in, and a difference thereof is calculated.

This difference is corresponding to an offset amount from a zero levelof the TE signal center, that is, a balance drift amount in adifferential circuit and the like for generating the TE signal. In thisembodiment, these offset amounts are obtained for a plurality ofsamples, and an averaged amount thereof is assumed to be the centerlevel of the TE signal (Step S25). The defined time T4 is set to a timeat which the sample value of the TE signal enough to detect the averagecenter level can be taken in. This detecting operation of the centerlevel of the TE signal is repeated until the counted time by the timerreaches the defined time T4 at a step S26 (NO). In a case that thecounted time by the timer exceeds the defined time T4 at the step S26(YES), the operation flow proceeds to a step S27. Then, a trackingbalance is adjusted through the TRBL circuit 43 such that the TRCLbecomes the zero level on the basis of the offset amount determined atthe step S25.

Next, the operation flow proceeds to a step S28, and this causes thetimer to start the counting operation for the defined time T5. Next, theoperation flow proceeds to a step S29, and the TEp-p is taken in whichis the maximum amplitude value of the TE signal. This take-in operationis repeated until the counted time T by the timer reaches the definedtime T5 (Step S30: NO). At this time, an averaging process is performedfor the maximum amplitude values which are repeatedly taken in. In acase that the counted time T by the timer exceeds the defined time T5 atthe step S30 (YES), the operation flow proceeds to a step S31, and thetracking gain is adjusted. The gain value to be adjusted is determinedby the maximum averaged amplitude value of the TE signals determined atthe step S29. That is, the servo gain is set such that the maximumaveraged amplitude value becomes a predetermined amplitude value. Next,the operation flow proceeds to a step S32, and the servo close signal isoutputted by the servo controller 38 such that the tracking servo loopis made close. The PWM 36 generates a pulse signal for driving atracking coil on the basis of the output signal from the TGA 34, thatis, the tracking error signal, corresponding to the servo close signaloutputted by the servo controller 38.

In this way, since the PWM 36 becomes active, the tracking servo loop ismade close. Next, the operation flow proceeds to a step S33 in FIG. 6.Then, the various adjustment values (the maximum amplitude value of thefocus error signal, the adjustment value of the focus gain, the centerlevel of the tracking error signal, the adjustment value of the trackingbalance, the maximum amplitude value of the tracking error signal, theadjustment value of the tracking gain and the like) in relation to thefocus servo and the tracking servo to the first layer determined at thesteps S1 to S32 are stored in predetermined addresses to store theinformation of the first layer in the RAM 42. Incidentally, the exampleof setting the servo gain has been explained in this embodiment.However, it is possible to change the gain as well as an equalizer valuecorresponding to each of the record layers to thereby optimize it. Atthis time, the equalizer value is also stored in the RAM 42.

Next, the operation flow proceeds to a step S34, and parameters, countervalues and the like are initialized which are used to determine thedefined values to the first layer. Next, the operation flow proceeds toa step S35, and the lens is moved down to a defined position. Then, oneis added to the value N indicative of the repetition number of the up ordown actions of the lens, and the lens is moved up at the defined speed(Steps S36 and S37). Next, at a step S38, it is judged whether or notthe FE value complying with the condition of FE1≧TH is obtainedsimilarly to the step S7. If it is not obtained (Step S38: NO), theoperation flow returns to the step S37, and the lens is continued to bemoved up.

On the other hand, if the FE value is obtained (Step S38: YES), theoperation flow proceeds to a step S39, and this causes the timer tostart the counting operation for the defined time T6. After the elapseof the defined time T6 at a step S40 (YES), the operation flow proceedsto a step S41, and it is performed to detect the FE value equal to ormore than the threshold TH.

The FE value detected at this step S41 indicates the FE2 of the secondlayer when the lens is moved up. At a time point when an amplitude valueof the FE2 crosses the TH level, this causes the timer to start thecounting operation for the defined time T7 (Step S42). Next, the maximumamplitude value FEp-p of the FE2 at N=a first time is read out and takenin at a step S43, and stored in the RAM 42. Then, at a step S44, it isjudged whether or not the counted time by the timer exceeds the definedtime T7. If it is judged that the counted time does not exceed thedefined time T7 (Step S44: NO), the lens is continued to be moved upuntil the counted time by the timer reaches the defined time T7. If itreaches the defined time T7 (Step S44: YES), the operation flow proceedsto a step S45, and one is added to the N. Further, the lens is moveddown at a step S46.

Next, the operation flow proceeds to a step S47, and it is judgedwhether or not the FE value in the second layer determined when the lensis moved down is equal to or more than the threshold TH. If the FE valueis equal to or less than the threshold TH (Step S47: NO), this indicatesthat the FE resulting from the 0 order light is not obtained yet in theoutput of the RF Amp 23. Thus, the operation flow returns to the stepS46, and the lens is continued to be moved down. If the FE value exceedsthe threshold TH (Step S47: YES), the operation flow proceeds to a stepS48. This causes the timer to start the counting operation for thedefined time T8. Then, the maximum amplitude value FEp-p at N=a secondtime is taken in at a step S49, and stored in the RAM 42. At a step S50,it is judged whether or not the counted time T by the timer exceeds thedefined time T8. If it exceeds the defined time T8 (step S50: YES), theoperation flow proceeds to a step S51, and the number N that the lens ismoved up and down is monitored. If the number N is less than 4 (StepS51: NO), the operation flow returns to the step S36, and then themaximum amplitude value of the FE2 associated with the up and downaction of the lens is continued to be taken in.

On the other hand, if the number N exceeds 4 (Step S51: YES), theoperation flow proceeds to a step S52, and the focus gain is adjustedfor the second layer. At this time, the adjusted gain value isdetermined by the maximum amplitude value of the FE2, in the up and downaction of the lens, which is stored in the RAM 42 at the steps S43 andS49. For example, in a case that the up and down action of the lens isperformed four times, the maximum amplitude values of the FE1s of thefour samples are stored in the RAM 42. Thus, an average value of themaximum amplitude values of the four samples is calculated, and then theservo gain is set such that this average value becomes a predeterminedamplitude value.

Next, after the lens is moved up (step S53) to a position at which theFE2 of the second layer is adjacent to a zero-cross point, the servoclose signal is outputted by the servo controller 38 (Step S54). The PWM29 generates the pulse signal for driving the focus coil on the basis ofthe output signal from the FGA 27, that is, the focus error signal,corresponding to the servo close signal outputted by the servocontroller 38. In this way, since the PWM 29 becomes active, the focusservo loop is made close (Step S54). Then, the operation flow proceedsto a step S55, and this causes the timer to start the counting operationfor the defined time T9. Next, in order to detect the center level(TRCL) of the tracking error (TE) signal, for example, the maximum peakvalue of the TE signal is taken in, and a difference thereof iscalculated. This difference is corresponding to the offset amount fromthe zero level of the TE signal center, that is, the balance driftamount in the differential circuit for generating the TE signal.

In this embodiment, these offset amounts are determined for a pluralityof samples, and the averaged amount thereof is assumed to be the centerlevel of the TE signal (Step S56). The defined time T9 is set to thetime at which the sample values of the TE signal enough to detect theaverage center level can be taken in. This detecting operation of thecenter level of the TE signal is repeated until the counted time by thetimer reaches the defined time T9 at a step S57. In a case that thecounted time by the timer exceeds the defined time T9 at the step S57(YES), the operation flow proceeds to a step S58, and then the trackingbalance is adjusted through the TRBL circuit 43 such that the TRCLbecomes the zero level on the basis of the offset amount determined atthe step S56.

Next, the operation flow proceeds to a step S59, and this causes thetimer to start the counting operation for the defined time T10. Next,the operation flow proceeds to a step S60, and the TEp-p is taken inwhich is the maximum amplitude value of the TE signal. This take-inoperation is repeated until the counted time T by the timer reaches thedefined time T10 (Step S61). At this time, the averaging process isperformed for the maximum amplitude values which are repeatedly takenin. In a case that the counted time T by the timer exceeds the definedtime T10 at the step S61 (YES), the operation flow proceeds to a stepS62, and the tracking gain is adjusted. The gain value to be adjusted isdetermined by the maximum averaged amplitude value of the TE signalsdetermined at the step S60. That is, the servo gain is set such that themaximum averaged amplitude value is the predetermined amplitude value.

Next, the operation flow proceeds to a step S63, and the servo closesignal is outputted by the servo controller 38 such that the trackingservo loop is made close. The PWM 36 generates the pulse signal fordriving the tracking coil on the basis of the output signal from the TGA34, that is, the tracking error signal, corresponding to the servo closesignal outputted by the servo controller 38. In this way, since the PWM36 becomes active, the tracking servo loop is made close. Next, theoperation flow proceeds to a step S64. Then, the various adjustmentvalues (the maximum amplitude value of the focus error signal, theadjustment value of the focus gain, the center level of the trackingerror signal, the adjustment value of the tracking balance, the maximumamplitude value of the tracking error signal, the adjustment value ofthe tracking gain and the like) in relation to the focus servo and thetracking servo to the second layer determined at the steps S34 to S63are stored in predetermined addresses to store the information of thesecond layer in the RAM 42.

Thanks to the operations at the steps S33 to S64, the adjustment valuesin relation to the optimal focus servo for the respective record layersin the two-layer disk are stored in predetermined addressescorresponding to the respective record layers in the memory RAM 42.Next, in order to transfer the pickup to a start position (for example,the innermost circumference track of the first layer) of the recordinformation recorded on the two-layer disk, after reading out theadjustment values of the first layer stored in the predeterminedaddresses of the RAM 42 (Step S65), a focus jump operation is performedat a step S66. That is, a focal position of the reading beam is shiftedfrom the record layer of the second layer to that of the first layer, orfrom the record layer of the first layer to that of the second layer.The initial operation (setup operation) to the two-layer disk 20 loadedon the reproducing apparatus is completed in accordance with the abovementioned operations (step S67).

Incidentally, the focus jump operation is performed as described below.At first, the tracking servo loop is made close. Then, the focus servoloop is made open. After the lens is forced to be transferred in a focusdirection (a direction vertical to the disk record surface) by apredetermined length (a distance between the layers), the closing actionof the focus servo is performed. The closing action of the trackingservo is successively performed, and the pickup is moved to search to adesired track as the occasion demands. In this way, after the focusservo and the tracking servo are once made open in conjunction with thefocus jump, when they are again made close, the adjustment values areused which correspond to the record layer of a jumped destination readout from the RAM 42. Thus, even during reproducing, in a case ofperforming the jump operation from the record layer in the first layerto that in the second layer or the record layer in the second layer tothat in the first layer, it is possible to read out the variousadjustment values corresponding to the record layer at the jumpeddestination from the RAM 42 prior to the jump operation to therebyadjust the servo gain on the basis of the read adjustment values in theservo closing operation after the jump operation. As a result, it ispossible to quickly perform the stable servo control.

[IV] Second Embodiment of the Invention

In a second embodiment of the present invention, focus error signals aresuccessively extracted, which are generated from the first and secondlayers, among focus error signals generated by applying the UP or DOWNoperation to the objective lens while emitting light beams to theone-sided two-layer disk loaded on the disk loading surface of thereproducing apparatus. A gain value is set for a focus servo on thebasis of each of these focus error signals. After that, a gain valuesetting is performed for a tracking servo on the basis of a trackingerror signal of the first layer. Next, a focus jump is performed to thesecond layer, and a gain value setting is performed for a tracking servoon the basis of a tracking error signal of the second layer. The abovementioned operation is also performed as a setup (initial setting)operation prior to the actual reproduction operation.

An operation of the second embodiment according to the present inventionis explained with reference to the block diagram of FIG. 1, operationtime charts in FIGS. 7A to 7C and flow charts of FIGS. 8 and 9.

At first, FIG. 7A shows two focus error signals (FE) detected by theoptical pickup 22 when the lens is moved up and down (in a case of twolayers). In FIG. 7A, a symbol N indicates a number at which the lens ismoved up and down. As shown in FIG. 7A, T1 is a time required from atime point when the amplitude voltage of FE1 (of the first layer)firstly generated since the up action of the lens exceeds a definedthreshold TH stored in the ROM 39 of the multiple layer disk type of thereproducing apparatus, until a time point corresponding to an end of theFE1. T2 is a time required from a time point when an amplitude voltageof the FE2 (of the second layer) exceeds the threshold TH, until a timepoint when the lens is moved up to the maximum set position.

T3 is a time required from a time point when the amplitude voltage ofthe FE2 (of the second layer) exceeds the threshold TH until a timepoint corresponding to an end of the S-shaped characteristics of theFE2, as for the case of moving down the lens. T4 is a time required froma time point when the amplitude voltage of the FE1 (of the first layer)exceeds the threshold TH, until a time point when the lens is moved downto the maximum set position. In FIG. 7B, T5 is a time required for atracking balance adjustment to be firstly performed for the first layer,and T6 is a time required for a tracking gain adjustment for the firstlayer. Similarly in FIG. 7C, T7 is a time required for a trackingbalance adjustment for the second layer, and T8 is a time required for atracking gain adjustment for the second layer.

The operation of the second embodiment according to the presentinvention is explained with reference to flow charts shown in FIGS. 8and 9.

At first, it is judged at a step S101 whether or not the optical disk isset. If the optical disk is set (step S101: YES), various data set whenpreviously reproducing the optical disk is initialized at a step S102.That is, values of counters and timers (which are not shown) are resetwhich are incorporated within the multiple-layer disk type of thereproducing apparatus used from now.

A disk discrimination of various disks is performed at a step S103. Theoperation of the disk discrimination is explained later in detail. Thelens is moved down to a defined position at a step S104. Then, the lensis moved up at a defined speed at a step S105. At a step S106, a numberN that the lens is repeated to be moved up and down is counted, and anumber M that the FE is taken in is counted. Then, at a step S107, adefined threshold TH, which is stored in advance in the ROM 39 of themultiple-layer disk type of the reproducing apparatus, is compared withthe obtained FE value. In a case that the FE value is not obtained (stepS107: NO), the lens is continued to be moved up. If the obtained FE1complies with FE1≧TH (step S107: YES), the operation flow proceeds to astep S108. The timer starts a counting operation for the time T1.

This counting operation in the timer for the defined time T1 is startedat a time point when the amplitude of the FE1 crosses (exceeds) the THlevel. The defined time T1 is set in the ROM 39 etc. in advance as atime until the first FE is finished. Next, the maximum amplitude valueFEp-p of the FE of the first layer is taken in at a step S109, andstored in the RAM 42. At a step S110, it is judged whether or not thecounted time by the timer exceeds the defined time T1. If it is judgedthat the counted time does not exceed the defined time T1 (Step S110:NO), the lens is continued to be moved up until the counted time by thetimer reaches the defined time T1. If it reaches the defined time T1(Step S110: YES), the operation flow proceeds to a step S111. One isadded to the number M, and the operation flow proceeds to a step S112.Then, it is judged whether or not the FE value of the second layer isequal to or more than the threshold TH. If the FE value is less than thethreshold TH (Step S112: NO), the moving up operation of the lens iscontinued until the FE value exceeds the threshold TH. If the FE valueexceeds the threshold TH (Step S112: YES), the operation flow proceedsto a step S113.

At a step S113, the timer starts the counting operation for the definedtime T2. Then, the maximum amplitude value FEp-p of the FE of the secondlayer is taken in at a step S114, and stored in the RAM 42. At a stepS115, it is judged whether or not the counted time by the timer exceedsthe defined time T2. in a case where it is judged at the step S115 thatthe counted time T by the timer reaches the defined time T2 (step S115:YES), the operation flow proceeds to a step S116, and the lens is moveddown. Then, one is added to each of the numbers N and M at a step S117.Next, at a step S118, it is judged whether or not the FE value of thesecond layer is equal to or more than the threshold TH. If the FE valueis less than the threshold TH (step S118: NO), it is continued to movedown the lens until the FE value exceeds the threshold TH. If the FEvalue exceeds the threshold TH (step S118: YES), the operation flowproceeds to a step S119, and the timer starts the counting operation forthe defined time T3. Then, the maximum amplitude value FEp-p of the FEof the second layer is taken in, and stored in the RAM 42 at a stepS120. Then, at a step S121, it is judged whether or not the counted timeT by the timer exceeds the defined time T3. If it exceeds the definedtime T3 (step S121: YES), the operation flow proceeds to a step S122,and one is added to the number M.

Next, at a step S123, it is judged whether or not the FE value of thefirst layer is equal to or more than the threshold TH. If the FE valueis less than the threshold TH (step S123: NO), it is continued to movedown the lens until the FE value exceeds the threshold TH. If the FEvalue exceeds the threshold TH (step S123: YES), the operation flowproceeds to a step S124, and the timer starts the counting operation forthe defined time T4. Then, the maximum amplitude value FEp-p of the FEof the first layer is taken in, and stored in the RAM 42 at a step S125.Then, at a step S126, it is judged whether or not the counted time T bythe timer exceeds the defined time T4. If it exceeds the defined time T4(step S126: YES), the operation flow proceeds to a step S127, and thenumber N that the lens is repeated to be moved up and down is monitored.If the number N is less than 4 (step S127: NO), the operation flowreturns to the step S105.

On the other hand, if the number N exceeds 4 (Step S127; YES), theoperation flow proceeds to a step S128, and the focus gains are adjustedfor the first and second layers. Then, at a step S129, the adjustedfocus gains for the first and second layers are stored into the RAM 42.After that, the lens is moved up at a step S30. Then, at a step S31, thePWM 29 generates a pulse signal for driving a focus coil on the basis ofthe output signal from the FGA 27, and the focus servo loop is madeclose by the servo controller 38.

Then, the operation flow proceeds to a step S132, and this causes thetimer to start the counting time for the defined time T5. Next, in orderto detect a center level (TRCL) of the tracking error (TE) signal, forexample, the maximum peak value and the minimum Peak value of the TEsignal are taken in, and a difference thereof is calculated (step S133)in FIG. 9. This difference is corresponding to an offset amount from azero level of the TE signal center, that is, a balance drift amount in adifferential circuit and the like for generating the TE signal.

In this embodiment, these offset amounts are obtained for a plurality ofsamples, and an averaged amount thereof is assumed to be the centerlevel of the TE signal (Step S133). The defined time T5 is set to a timeat which the sample value of the TE signal enough to detect the averagecenter level can be taken in. This detecting operation of the centerlevel of the TE signal is repeated until the counted time by the timerreaches the defined time T5 at a step S134 (NO). In a case that thecounted time by the timer exceeds the defined time T5 at the step S134(YES), the operation flow proceeds to a step S135. Then, a trackingbalance is adjusted through the TRBL circuit 43 such that the TRCLbecomes the zero level on the basis of the offset amount determined atthe step S133.

Next, the operation flow proceeds to a step S136, and this causes thetimer to start the counting operation for the defined time T6. Next, theoperation flow proceeds to a step S137, and the TEp-p is taken in whichis the maximum amplitude value of the TE signal. This take-in operationis repeated until the counted time T by the timer reaches the definedtime T6 (Step S138: NO). At this time, an averaging process is performedfor the maximum amplitude values which are repeatedly taken in. In acase that the counted time T by the timer exceeds the defined time T6 atthe step S138 (YES), the operation flow proceeds to a step S139, and thetracking gain is adjusted. The gain value to be adjusted is determinedby the maximum averaged amplitude value of the TE signals determined atthe step S137. That is, the servo gain is set such that the maximumaveraged amplitude value becomes a predetermined amplitude value. Next,the adjusted tracking gain for the first layer is stored into the RAM 42at a step S140. Then, the focus jump operation is performed at a stepS141. That is, a focal position of the reading beam is shifted from therecord layer of the first layer to that of the second layer.

Next, after the lens is moved up to a position at which the FE2 of thesecond layer is adjacent to a zero-cross point, the servo close signalis outputted by the servo controller 38 (Step S142). The PWM 29generates the pulse signal for driving the focus coil on the basis ofthe output signal from the FGA 27, that is, the focus error signal,corresponding to the servo close signal outputted by the servocontroller 38. In this way, since the PWM 29 becomes active, the focusservo loop is made close (Step S142). Then, the operation flow proceedsto a step S143, and this causes the timer to start the countingoperation for the defined time T7. Next, in order to detect the centerlevel (TRCL) of the tracking error (TE) signal, for example, the maximum peak value of the TE signal is taken in, and a difference thereof iscalculated. This difference is corresponding to the offset amount fromthe zero level of the TE signal center, that is, the balance driftamount in the differential circuit for generating the TE signal.

In this embodiment, these offset amounts are determined for a pluralityof samples, and the averaged amount thereof is assumed to be the centerlevel of the TE signal (Step S144). The defined time T7 is set to thetime at which the sample values of the TE signal enough to detect theaverage center level can be taken in. This detecting operation of thecenter level of the TE signal is repeated until the counted time by thetimer reaches the defined time T7 at a step S145. In a case that thecounted time by the timer exceeds the defined time T7 at the step S145(YES), the operation flow proceeds to a step S146, and then the trackingbalance is adjusted through the TRBL circuit 43 such that the TRCLbecomes the zero level on the basis of the offset amount determined atthe step S144.

Next, the operation flow proceeds to a step S147, and this causes thetimer to start the counting operation for the defined time T8. Next, theoperation flow proceeds to a step S148, and the TEp-p is taken in whichis the maximum amplitude value of the TE signal. This take-in operationis repeated until the counted time T by the timer reaches the definedtime T8 (Step S149). At this time, the averaging process is performedfor the maximum amplitude values which are repeatedly taken in. In acase that the counted time T by the timer exceeds the defined time T8 atthe step S49 (YES), the operation flow proceeds to a step S150, and thetracking gain is adjusted. The gain value to be adjusted is determinedby the maximum averaged amplitude value of the TE signals determined atthe step S148. That is, the servo gain is set such that the maximumaveraged amplitude value is the predetermined amplitude value. Next, theoperation flow proceeds to a step S151, and the servo close signal isoutputted by the servo controller 38 such that the tracking servo loopis made close. The PWM 36 generates the pulse signal for driving thetracking coil on the basis of the output signal from the TGA 34, thatis, the tracking error signal, corresponding to the servo close signaloutputted by the servo controller 38.

In this way, since the PWM 36 becomes active, the tracking servo loop ismade close. Next, at a step S152, the adjusted tracking gain for thesecond layer is stored. Finally, the setup of the multiple layer disksubstrate is ended (step S53).

In the second embodiment, although the explanations have been made for acase where only the gains for focusing and tracking are adjusted andstored, it is also possible in the second embodiment that the equalizervalues etc. can be adjusted and stored in the same manner as the firstembodiment.

In this way, according to the second embodiment, it is possible to morespeedily set the gain value than the first embodiment, since the focuserror signals for obtaining the loop gain value of the focus servo loopof each layer are all taken in by one up and down movement of the lens.

[V] Third Embodiment of the Invention

Although the focus jump is performed to the second layer in order toextract the tracking error signal of the second layer in the case of thesecond embodiment of the present invention, a third embodiment of thepresent invention is a method of setting the focus and tracking gainvalues in the first and second layers without performing the focus jump.

The third embodiment of the present invention is explained withreference to the block diagram of FIG. 1 and the flow charts of FIGS. 8to 10.

In the third embodiment, the steps S101 to S132 in FIG. 8 and the stepsS133 to S140 in FIG. 9 as for the processes of adjusting the focus gainvalue for the first layer, the focus gain value for the second layer andthe tracking gain value for the first layer in the second embodiment areperformed at first.

From the step S140 of FIG. 9, the operation flow proceeds to a step S241in FIG. 10. In FIG. 10, the same steps as those in FIG. 9 carry the samereference numerals and the explanations thereof are omitted.

At a step S241, the servo controller 38 determines a ratio of theaverage value of the maximum amplitude values of the focus errors of thefirst layer to the average value of the maximum amplitude values of thefocus errors of the second layer, for example, among the FEp-p valuestaken in at the steps S109, S114, S120 and S125. Then, it is stored inthe RAM 42 as a value A. Next, at a step S242, the tracking gain for thesecond layer is calculated by multiplying the value A stored at the stepS241 by the tracking gain value for the first layer, and is stored inthe RAM 42 as the tracking gain value for the second layer at a stepS243.

As mentioned above, since the tracking gain for the second layer isdetermined on the basis of the ratio of the amplitude values of thefocus errors in the respective layers, it is possible to save theadjusting time for the tracking gain for the second layer. Although theratio is calculated on the basis of the amplitude values of the focuserrors in the respective layers in this embodiment, it is naturallypossible to get the same effect, even if calculating the ratio from thevalues of the focus gains in the respective layers stored at the stepS129.

Although the third embodiment of the present invention has beenexplained as the variation of the second embodiment, the method of thethird embodiment of the present invention can be also applied to thefirst embodiment of the present invention. That is, after the focus jumpis performed to the,second layer, the focus error signal obtained fromthe second layer is extracted, and the gain is set. After that, themethod of the third embodiment of the present invention can be used inthe tracking.

[VI] Disk Discrimination Method of the Invention

The disk discrimination method used in the above mentioned flow chartsis represented by a lens exchanging type of a disk discrimination methodshown in a flow chart of FIG. 11, and by a disk discrimination method ofusing a bifocal lens shown in a flow chart of FIG. 12.

(1) Lens Exchanging Type of Disk Discrimination Method

At first, in FIG. 11, a lens 1 is set to the optical pickup at a stepS301. Next, at a step S302, the lens is moved up to a defined position.After that, the lens is moved down at a defined speed at a step S303. Ata step S304, a focus error signal is detected, and the obtained FE valueis compared with a threshold TH1 that is one of predeterminedthresholds. If the obtained FE value exceeds the threshold TH1 (stepS304: YES), the focus error signal is again detected at a step S305. Atthe step S305, a threshold TH2 that is another one of the predeterminedthresholds is compared with the FE, separately from the step S304.

The two thresholds TH1 and TH2 are defined on the basis of thedifference between the maximum amplitude values of the FEs generated inthe CD and the DVD at a time of using the lens 1 respectively. That is,the threshold TH1 is used for the CD, and the threshold TH2 is used forthe DVD. Therefore, in a case that the loaded optical disk is the DVD,it complies with a condition of FE≧|TH1| at the step S304. On the otherhand, if it does not comply with a condition of FE≧|TH2| at the stepS305 (NO), it is discriminated as the CD. Moreover, at a step S306, itis required to set D=2, and the operation flow proceeds to a step S312.Then, the down action of the lens is stopped. If it complies with thecondition of FE≧|TH2| at the step 5305 (YES), it is judged as the firstlayer of the DVD, and thereby D=1 is set at a step S307. After that, thetimer T2 is set at a step S308. This timer T2 is set to this requiredvalue, since it waits for a time when the S shape in the first layer iscompleted, in a case of the multiple-layer disk.

A generation time of the FE is monitored at a step S309. If the FEexceeding the threshold TH2 is again generated at a step S310, it isdiscriminated as the two-layer disk at a step S311, and D=3 is set. Ifit complies with a condition of T2≧t at the step S309 (YES), this meansthat there is no S shape of the FE in the second layer. Thus, theoperation flow proceeds to the step S312, and then the down action ofthe lens is stopped. The value D is checked at a step S313 (YES), sothat if D=1, it is discriminated as a one-layer disk of 0.6 mm. Or, ifD=3 at the step S313 (YES), it is discriminated as a two-layer disk of0.6 mm. So, the disk discrimination is finished at a step S315. If D=2at the step S313 (NO), it is discriminated as a 1.2 mm disk. So, thelens 2 is set at a step S314, and the disk discrimination is finished atthe step S315.

(2) Disk Discrimination Method When Using Bifocal Lens

FIG. 12 shows a disk discrimination method in a case of using thebifocal lens. In FIG. 12, the lens is firstly moved up to a definedposition at a step S401. After that, the lens is moved down at a definedspeed at a step S402. At a step S403, a focus error signal is detected,and the obtained FE is compared with a threshold TH1 that is one ofpredetermined thresholds. If the obtained FE value exceeds the thresholdTH1 (step S403: YES), the focus error signal is again detected at a stepS404. At the step S404, a threshold TH2 that is one of the predeterminedthresholds is compared with the FE, separately from the step S403. Thetwo thresholds TH1 and TH2 are defined on the basis of the differencebetween the maximum amplitude values of the FEs generated by the 0 orderlight or the +1 order light in the CD and the DVD at a time of using thebifocal lens respectively.

That is, the threshold TH1 is used for the CD, and the threshold TH2 isused for the DVD. Thus, in a case that the loaded optical disk is theDVD, it complies with the condition of FE≧|TH1| at a step S403 (YES). Ifit does not comply with the condition of FE≧|TH2| at a step S404 (NO),it is discriminated as the CD. At a step S405, it is required to setD=2, and the operation flow proceeds to a step S411. Then, the downaction of the lens is stopped. If it complies with the condition ofFE≧|TH2| at the step S404 (YES), it is judged as the first layer of theDVD, and thereby D=1 is set at a step S406. After that, the timer T2 isset at a step S407. This timer T2 is set to this required value, sinceit waits for the time when the S shape in the first layer is completed,in a case of the multiple-layer disk.

A generation time of the FE is monitored at a step S408. If the FEexceeding the threshold TH2 is again generated at a step S409 (YES), itis discriminated as the two-layer disk at a step S410, and D=3 is set.If it complies with the condition of T2≧t at the step S409, this meansthat there is no S shape of the FE of the second layer. Thus, theoperation flow proceeds to a step S411, and then the down action of thelens is stopped. The value D is checked at a step S412. If D=1, it isdiscriminated as the one-layer disk of 0.6 mm. Or, if D=3, it isdiscriminated as the two-layer disk of 0.6 mm. So, the diskdiscrimination is finished at a step S412.

The CD, the DVD (one-layer) and the DVD (two-layer) are discriminated bythe above mentioned disk discrimination method. The DVD (two-layer) isused in this embodiment, for example.

[VII] Fourth Embodiment of the Invention

A fourth embodiment of the present invention is a method of setting thefocus and tracking gain values as well as the gain value for the RFsignal.

FIGS. 13 and 14 show flow charts in which the gain for the RF signal isadjusted, and show portions that are not included in the flow chartsused in the first and second embodiments of the present invention. Atfirst, the fourth embodiment is explained with reference to FIG. 13. Ata step S501, the focus gains for the first and second layers areautomatically adjusted as indicated in the above mentioned embodiments.Then, the focus loop of the first layer is made close at a step S502.After that, the tracking gain for the first layer is adjusted at a stepS503. Then, the tracking loop is made close at a step S504. The maximumamplitude value of the RF signal of the first layer is taken in at astep S505. The gain value is calculated by the RGA 48 and the servocontroller 38, and stored in the RAM 42 at a step S506.

Next, the focus and tracking loops are made open at a step S507. Theoperation flow proceeds to the second layer at a step S508. Sinceoperations at the steps S509 to S513 for the second layer are similar tothose at the steps S503 to S507 for the first layer, the explanationsthereof are omitted.

After that, the focus gain value, the tracking gain value and the RFgain value for the first layer stored in the RAM 42 are read out at astep S514. Then, the focus is again made open and the jump is performedto the first layer at a step S515. The focus and tracking loops are madeclose at a step S516. At a step S517, the multiple-layer disk type ofthe reproducing apparatus is made in a play state so as to perform areproduction. If the reproduction of the loaded disk is completed or astop command is issued at a step S518 (YES), the operation is ended. Onthe other hand, when the stop command is not issued at the step S518(NO), and if a command to jump to another layer is issued at a step S519(YES), the tracking and focus loops are made open at a step S520, andthe focus gain value, the tracking gain value and the RF gain value foranother layer are read out at a step S521. Then, the jump to anotherlayer is performed at a step S522, and the operation flow returns to thestep S517 so as to perform the play of the multiple-layer. If the playis completed (step S18: YES), the reproduction is ended.

As mentioned above, since the gain values for the RF signals in therespective layers are also set and stored, it is possible to make therespective servos stable at a time of reproducing to thereby accuratelyreproduce the signal.

[VIII] Fifth Embodiment of the Invention

A fifth embodiment of the present invention is a method of taking in themaximum amplitude signal of the RF signal without making the trackingloop close, as a modification of the fourth embodiment of the presentinvention.

The fifth embodiment of the present invention is explained withreference to FIG. 14. Since operations at steps S601 to S603 are same asthe steps S501 to 503 of FIG. 13, the explanations thereof are omitted.At a step S604, the maximum amplitude value of the RF signal of thefirst layer is read while the tracking open state is kept. Then, thegain is calculated by the RGA 48 and the servo controller 38, and storedin the RAM 42 at a step S605.

Next, the focus loop is made open at a step S606, and the jump to thesecond layer is performed at a step S607. Since operations of steps S608to S610 for the second layer are similar to those of steps S603 to S605for the first layer, the explanations thereof are omitted. After that,the focus loop is made open at a step S611. Then, the focus gain value,the tracking gain value and the RF gain value for the first layer storedin the RAM 42 are read out at a step S612. The jump to the first layeris performed at a step S613, and the focus and tracking loops are madeclose at a step S614. Since operations at steps S615 to S620 are thesame as to those at the steps S517 to S522 in FIG. 13, the explanationsthereof are omitted.

As mentioned above, in the fifth embodiment of the present invention,the maximum amplitude values of the RF signals in the respective layersare taken in while the tracking is kept in the open state. Thus, theadjustment time is shorter than that of the fourth embodiment of thepresent invention to thereby make the setting operation quicker.

[IX] Sixth Embodiment of the Invention

A sixth embodiment of the present invention is a method of preparing andstoring a set value of the gain value for the RF signal for each diskand each layer in advance, as a modification of the fifth embodiment ofthe present invention.

The sixth embodiment of the present invention is explained withreference to FIG. 15. Since operations at steps S701 to S703 are thesame as those at the steps S601 to 603 of FIG. 14, the explanationsthereof are omitted. At a step S704, the gain value for the RF signal ofthe first layer is read and set, which is stored in the ROM 39 inadvance as defined value for each disk and each layer. The focus loop ismade open at a step S705, and the jump to the second layer is performedat a step S706. After the tracking gain is adjusted at a step S707, thegain value for the RF signal of the second layer is read and set, whichis stored in the ROM 39 in advance, similarly to the case of the firstlayer, at a step S708. The focus loop is made open at a step S709, andthe jump to the first layer is performed at a step S710. Then, the focusgain value, the tracking gain value and the RF gain value for the firstlayer stored in the RAM 42 are read out at a step S711. Then, the focusand tracking loops are made close at a step S712. Operations on andafter a step S713 are the same as those at the steps S615 to S620 inFIG. 14. Thus, the explanations thereof are omitted.

As mentioned above, in the sixth embodiment of the present invention,the gain value for the RF signal is prepared and stored as a set valuefor each disk and each layer in advance. Thus, the adjustment time isshorter than that of the fifth embodiment of the present invention tothereby make the setting operation quicker.

Although the example of adjusting the focus and tracking gains as wellas the RF gain has been explained in the embodiments, it is naturallypossible to adjust only the RF gain. Further, it is allowable to:extract a signal in a particular frequency band, for example, 3T(minimum time width) through the RGA 48 and the servo controller 38 orextract only the 3T through the BPF (Band Pass Filter); perform an A/Dconversion thereof; take in a level of the 3T; send it to the RGA 48;and make the level of at least the 3T frequency up, so as tosimultaneously perform the equalizer adjustment or perform only theequalizer adjustment. Accordingly, this enables an eye pattern of the RFsignal to be open, and a proper spindle servo to be performed, tothereby improve the signal reading capability.

In the embodiments, as shown in FIG. 13 or 14, the maximum amplitudevalue of the RF signal is read by the tracking close circuit/opencircuit, and thereby the gain of the RF signal is adjusted. However, ina case of generating the RF signal from a four-division light converter(not shown) within the optical pickup 22 similarly to the focus error,it is possible to read the maximum amplitude value of the focus errorsof the first and second layers and set and store the gain values for theRF signals of the respective layers from this value, to thereby achievethe similar effect.

More concretely, in this case, a standard value as for a level of the FEof a standard disk, for example, for each of layers, is stored in theRAM 42 in advance, and the standard value of each layer is compared withthe FE value of each layer, so that the gain value as a ratio to the RFsignal for each layer is set and stored.

Further, in the embodiments, the RF gains are adjusted and stored onlyfor the first and second layers of the two-layer disk. However, as forthe first layer disk of the DVD or the CD, it is also allowable toadjust, store and use the respective gain values for the focus, thetracking and the RF, and/or the equalizer value. Further, in a case ofmeasuring the focus and tracking gain values and/or the equalizer valueto thereby adjust and store them, the set value may be prepared inadvance for each disk and each layer with respect to the RF gain valueand/or the equalizer value, and stored in the ROM 39. Then, this setvalue may be used without performing the adjustment.

Furthermore, in order to cope with a flaw of a disk during measuring oradjusting the gain value and/or the equalizer value, the flaw detectingcircuit (not shown) may be separately mounted, so that the measurementcan be stopped until the flaw is solved, or the measurement can beperformed again.

Incidentally, in a case of producing a disk in which one pair of theabove mentioned two-layer disks are formed on both sides thereof, it ispossible to store the adjustment values in the respective record layersas well as surface discrimination information thereof so as to perform aquick correspondence even if a disk reproduction surface is changed.Further, by storing the information peculiar to the disk with theadjustment value, it is possible to discriminate the peculiarinformation at a time of reproducing, so as not to perform the initialsetting operation again with respect to the disk, to which the initialsetting operation has been once performed.

[X] Seventh Embodiment of the Invention

At first, a seventh embodiment of the present invention is explainedwith reference to FIGS. 16 to 21. Although an apparatus of thisembodiment is a DVD/CD compatible type of a reproducing apparatus, acase of reproducing the DVD as an information record medium is explainedin this embodiment.

FIG. 16 shows a block diagram indicating a schematic configuration ofthe reproducing apparatus of this embodiment. In FIG. 16, an opticaldisk 101 is the DVD as one example of the information record medium. Inthe optical disk 101, information is recorded on an information track byusing, for example, a phase pit or a magnetic record mark. An opticalspot is formed by light beams from a laser diode (not shown) included inan optical pickup 102 as one example of a reading device.

A reflection light of this optical spot is inputted to a receivingoptics such as a four-division photo detector (not shown) included inthe optical pickup 102 and the like, as a reflection light to whichastigmatism is given. A detection signal is outputted from the receivingoptics.

An RF Amplifier 103, which is a constitutional element of one example ofa reproduction process device, generates an RF (Radio Frequency) signalfrom the detection signal outputted by the receiving optics of theoptical pickup 102, and also outputs a focus error signal FE and atracking error signal TE.

This RF signal is inputted to a spindle driver 105 as a standard signalto achieve a synchronization for a spindle motor 106 after the RF signalis demodulated and corrected by a demodulation and correction circuit104, and is also inputted to a video circuit 107 and an audio circuit108, respectively, as a video signal and an audio signal. Accordingly, avideo output and an audio output can be generated, respectively.

On the other hand, the focus error signal FE and the tracking errorsignal TE are outputted from a servo circuit 110 controlled by a CPU 109as one example of a control device, to a focus driver 111 and a trackingdriver 112 as one example of a drive device, respectively, as a focusdrive signal FD and a tracking drive signal TD. Accordingly, a focusservo and a tracking servo are performed. The servo operation by thisservo circuit 110 is switched between a close state and an open state bya servo control signal FSON from the CPU 109. A gain up signal GUP formaking a servo sensibility higher is also outputted from the CPU 109 tothe servo circuit 110. Moreover, the focus drive signal FD and thetracking drive signal TD are controlled and outputted by the servocircuit 110 when the servo is close. A focus jump signal and arising/lowering signal of the focus are outputted by an output commandfrom the CPU 109 when the servo is open. For this reason, a RAM 113 inwhich a pulse width of the focus drive signal FD and the like are storedis connected to the CPU 109.

An operation panel 114 is connected to the CPU 109. Operationinformation, such as start or stop of the reproduction of the opticaldisk 1 and the like, are inputted through the operation panel 114 to theCPU 109. Incidentally, a signal for indicating whether or not theoptical disk 1 is loaded is also inputted to the CPU 109 through asensor and the like, although this mechanism is not shown in FIG. 16.

In a case of the reproducing apparatus of this embodiment having theabove mentioned configuration, it is necessary to jump an objective lensof the optical pickup 102 from one information record layer to anotherinformation record layer in order to reproduce the optical disk havingmultiple layers. This jump is performed by outputting a kick pulse asthe focus drive signal FD as shown in FIG. 17, to the focus driver 111.A kick pulse height i.e. peak to peal (p-p) value and a pulse width ofthis kick pulse are set from the viewpoints of an interval between theinformation record layers and a moving amount of the objective lens. Forexample, it is possible to make the peak value larger and the pulsewidth shorter, to thereby jump the objective lens to a target positionmore quickly.

In case of outputting the kick pulse, the servo control signal FSON isoutputted from the CPU 109 to the servo circuit 110 to thereby make theservo open, and then an output request of the focus drive signal FD isissued so as to output a kick pulse with a predetermined pulse width andpeak value to the servo circuit 110. Accordingly, a kick pulse as shownin FIG. 17 is outputted from the servo circuit 110 to the focus driver111. Then, the objective lens of the optical pickup 102 is jumped by apredetermined amount corresponding to a drive signal based on the kickpulse from the focus driver 111. If the objective lens is jumped, forexample, from a lower portion to an upper portion, it is moved upwardfrom a focal point by the kick pulse. Thus, for example, an upward focuserror signal FE is generated. Further, when it is faced to a focal pointin a second layer, a downward focus error signal FE is generated.Therefore, the focus is made close at a position at which this downwardfocus error signal FE is generated. So, the CPU 109 detects the zerocross of this focus error signal FE to thereby output the servo controlsignal FSON to the servo circuit 110 so as to make the servo close.Moreover, the CPU 9 outputs to the servo circuit 110 the gain up signalGUP for transiently making a focus gain larger, so as to stabilize thefocus coil at the jumped point. An output time for this gain up signalGUP is referred to as a gain up time.

Furthermore, in order to suddenly stop the optical pickup at the jumpedpoint, a brake pulse may be applied to the focus driver 111 as the focusdrive signal FD after the jump pulse, as shown in FIG. 18. Since amoving part is tried to be suddenly stopped also in this case, there maybe a possibility that a focus coil cannot become quickly stable. Thus,such a method is performed in which not only the brake pulse is applied,but also the focus gain is transiently made higher until it becomesstable.

As mentioned above, it is necessary to set the pulse width, the peakvalue, the brake pulse width and the gain up time to predeterminedvalues, in order to jump the optical pickup to thereby reproduce themultiple-layer disk. In a case that the interval between the informationrecord layers is not known, it is necessary to set an average pulsewidth, peak value, brake pulse width and gain up time and to output thekick pulse to thereby detect the zero cross signal of the focus errorsignal FE. Thus, in a case that these values are not appropriate, forexample, in a case that the interval between the layers is longer thanan average interval, and in other cases, an excess time is requireduntil the servo is made close.

However, by examining relations between the moving amount of theobjective lens and the pulse width, the peak value, the brake pulsewidth and the gain up time in advance, it is possible to select anappropriate pulse width and the like in accordance with the intervalbetween the layers to thereby jump the objective lens in the shortesttime.

Then, this embodiment is constituted so as to store in advance the pulsewidth, the peak value, the brake pulse width and the gain up time whichcorrespond to the several intervals between the layers, and measure theintervals between the layers in the information record layersimmediately after loading the optical disk and then read out the pulsewidth and the like corresponding to the measured interval between thelayers when switching between the information record layers, to therebyjump the objective lens of the optical pickup 102 to the target positionquicker and much accurate.

In this embodiment, the pulse width, the peak value, the brake pulsewidth and the gain up time which correspond to the interval between thelayers are measured in advance, and stored in a ROM and the like (whichare not shown) within the CPU 109 as a table. Then, the pulse width andthe like corresponding to the interval between the layers are selectedfrom the table at a predetermined time, and stored in the RAM 113. Thatis, the CPU 109 and the RAM 113 are used as one example of a selectiondevice and one example of a parameter memory respectively, in thisembodiment.

Next, a method of measuring the interval between the layers in thisembodiment is explained. At first, the optical pickup 102 used in theapparatus of this embodiment is explained in detail. The optical pickup102 of this embodiment comprises, for example, a bifocal lens as shownin FIG. 19.

The optical pickup 102 comprising this bifocal lens has a structure inwhich it is possible to emit two light beams focused on differentpositions on one straight line. That is, in the bifocal lens, adiffraction grating H and an objective lens R are arranged on oneoptical path, as shown in FIG. 19. Light beams made parallel to eachother by a collimator lens (not shown) are divided into three beams: a 0order light and ±1 order lights, by the diffraction grating H.Utilization of a difference between the optical path lengths of the 0order light and the +1 order light among them enables the 0 order lightand the +1 order light to be focused on the different positions on onestraight line.

Actually, the +1 order light is adapted to be focused on a fartherposition from the objective lens R than the 0 order light. The 0 orderlight is set so as to be optimally collected on the information recordsurface of the DVD, and further the +1 order light is set to beoptimally collected on the information record surface of the CD. Theutilization of the optical pickup having such a bifocal lens enables theapparatus of this embodiment to reproduce both of the CD and the DVD.

In the two light beams from the optical pickup 102 having the bifocallens, the +1 order light is set to be optimally collected on the CD, andthe 0 order light is set to be optimally collected on the DVD.Accordingly, the +1 order light is longer in focal length. Thus, forexample, as shown in FIG. 19, when the bifocal lens is moved up for themultiple-layer DVD, the +1 order light is firstly collected on a firstlayer of the information record surface of the DVD, and then a focuserror signal is detected. Next, it is collected on a second layer of theinformation record layer, and the similar focus error signal isdetected. A pseudo focus error signal is detected which is generatedsince a reflection light from the first layer of the +1 order light isrouted through an optical path of the 0 order light. Moreover, thesimilarly pseudo focus error signal is detected by a reflection lightfrom the second layer. Finally, a focus error signal is detected fromthe first layer corresponding to the 0 order light. Furthermore, a focuserror signal is also detected from the second layer.

As mentioned above, in the multiple-layer disk, a total of six focuserror signals are generated by using the optical pickup 102 having thebifocal lens. However, by setting a threshold TH which is larger than apeak value of the pseudo focus error signal and smaller than a peakvalue of the focus error signal for the 0 order light, a focus errorsignal exceeding the threshold TH is only the focus error signal for the0 order light. Thus, since a moving speed of the optical pickup isconstant, it is possible to measure an interval between the occurrencesof the bifocal error signals for this 0 order light to thereby measurean interval between the first layer and the second layer in theinformation record layers.

That is, a timer as one example of a time counting device is actuated ata time of detecting the focus error signal larger than the threshold TH.Then, the timer is stopped at a time of detecting a next focus errorsignal. Accordingly, it is possible to determine an interval between twosuccessive focus error signals. Assuming that a value determined by thetimer counting action is t, and that a constant based on the up and downmoving speed of the objective lens is a. Then, X=t/a is a value peculiarto an interval between layers. By the CPU 109 as one example of thecalculation device, for example, if X is defined by a followingexpression (1) as:

1.6≦X≦2.5  (1)

the interval between the layers is judged as 40 μm. Or, if X is definedby a following expression (2) as:

2.6≦X≦3.5  (2)

the interval between the layers is judged as 60 μm. When t=4 msec, andif a=2, the loaded disk is discriminated as a disk having an interval of40 μm since X=4 msec/2=2, in this example.

A measured interval between the focus error signals may be from a timepoint when the focus error signal exceeds the predetermined thresholdTH, to a time point when the next focus error signal exceeds thethreshold TH, as shown in FIG. 20A. Alternatively, by setting thethresholds at an upper side and a lower side as shown in FIG. 20B, themeasured interval may be from a time point when a first rising portionof the focus error signal exceeds the threshold at the upper side, to atime point when a second trailing portion of the focus error signaldrops below the threshold at the lower side.

Next, operations of the apparatus of this embodiment are explained withreference to FIGS. 19 and 21. Incidentally, respective processes shownin FIG. 21 are mainly performed by the CPU 109. Timers T1 and T2described later as one example of a time counting device are built inthe CPU 109.

As shown in FIG. 21, it is firstly judged whether or not the disk is set(Step S801). If the disk is judged to be set, a content of the RAM 113and the timers T1 and T2 are cleared, and a register and the likeincluded in the CPU 109 are initialized (Step S802). Next, the objectivelens is moved down to a lower limit shown in FIG. 19 (Step S803). Afterthe objective lens arrives at the lower limit, an operation of the timerT1 is started (Step S804) in order to check the arrival of the objectivelens to an upper limit. Moreover, the objective lens is moved up (StepS805). As for a focus error signal detected during the up action (referto FIG. 19), it is judged whether or not any of the peak values exceedsthe threshold TH (Step S806). If the peak value exceeds the threshold TH(Step S806: YES), an operation of the timer T2 is started (Step S807) inorder to measure a time required until a next peak value exceeds thethreshold TH. Next, it is judged whether or not the next peak valueexceeds the threshold TH (Step S808). If it exceeds (Step S808: YES),the operation of the timer T2 is finished (Step S809).

After that, the operation waits until the value of the timer T1 exceedsa predetermined value t1 (Step S810). If it exceeds (Step S810: YES), itis judged that the objective lens is moved to the upper limit. The timerT1 is stopped (Step S811), and the up action of the objective lens isstopped (Step S812).

The interval between the information record layers is determined fromthe aforementioned judgment expressions (1) and (2) on the basis of thevalue of the timer T2 (Step S813). At least one value among the pulsewidth, the peak value, the brake time and the gain up time for theoptimal kick pulse is selected from the table, on the basis of theinterval between the layers. Then, it is stored in the RAM 113 (StepS814).

Since the value to jump the objective lens is stored as mentioned above,unless the disk is replaced after that, it is possible to output acontrol signal to the servo circuit 110 on the basis of the stored valueto thereby jump the objective lens to a position suited for each of theinformation record layers accurately and quickly.

[XI] Eighth Embodiment

Next, an eighth embodiment of the present invention is explained withreference to FIGS. 22 and 23. Incidentally, identical reference numbersare assigned to parts common to the seventh embodiment. Then, theexplanations thereof are omitted.

In this embodiment, a disk discrimination is performed at the same timewhen the interval between the layers is measured as mentioned above. Forexample, it is discriminated that any of the one-layer DVD, themultiple-layer DVD and the CD is loaded. Thus, the CPU 109 functions asone example of a discrimination device in this embodiment.

Since a structure of a hardware of this embodiment is the same as thatof the seventh embodiment, the explanation thereof is omitted. Then, acontrol in this embodiment is explained with reference to FIGS. 22 and23.

As shown in FIG. 22, it is firstly judged whether or not the disk is set(Step S820). If the disk is judged to be set (YES), the followinginitializations are performed. That is, a content of the RAM 113 iscleared, and registers included in the CPU 109, for example, a registerD and a counter E described later are cleared (Step S821). Next, theobjective lens is moved down to a lower limit shown in FIG. 23 (StepS822). After the objective lens arrives at the lower limit, a theoperation of the timer T1 is started (Step S823) in order to check thearrival of the objective lens to an upper limit. Further, the objectivelens is moved up (Step S824). As for a focus error signal detectedduring the up action (refer to FIG. 23), it is judged whether or not anyof the peak values exceeds a threshold TH1 (refer to a symbol TH1 inFIG. 23) (Step S825). If the peak value exceeds the threshold TH1 (StepS825: YES), operations of the timers T2 and T4. are started (Step S826).

This timer T2 is used to measure the interval between the layers in acase that the loaded disk is the multiple-layer DVD, similarly to theseventh embodiment. The timer T4 is used to perform the discriminationbetween the one-layer DVD and the CD.

Next, it is judged whether or not a next peak value exceeds thethreshold TH1 (Step S827). Before the timer T1 reaches the predeterminedvalue t1, that is, when the objective lens does not arrive at the upperlimit (Step S828: NO), if it exceeds the threshold TH1 (Step S827: YES),the loaded disk can be discriminated as the two-layer DVD as shown inFIG. 23. Then, the operation of the timer T2 is finished similarly tothe seventh embodiment (Step S829). The operation waits until the valueof the timer T1 exceeds the predetermined value t1 (Step S830).

On the other hand, even if the timer T1 reaches the predetermined valuet1, when the peak does not exceed the threshold TH1 (Step S827 NO, andStep S828: YES), the loaded disk can be discriminated as the one-layerDVD or the CD as shown in FIG. 23. Then, the value of the timer T2 iscleared (Step S831).

If the timer T1 reaches the predetermined value t1 as mentioned above,it is judged that the objective lens arrives at the upper limit. Thus,the operation of the timer T1 is finished. Further, an operation of atimer T3 is started (Step S832) in order to check the arrival of theobjective lens to the lower limit. Then, the objective lens is startedto be moved down (Step S833).

It is judged whether or not the peak value again exceeds the thresholdTH1 (Step S834). If it exceeds the threshold TH1 (Step S834: YES), anoperation of a timer T4 is finished (Step S835). As shown in FIG. 23, aninterval t41 at which the FE peak values are generated in a case thatthe disk is the one-layer DVD is shorter than an interval t42 at whichthe FE peak values are generated in a case of the CD.

Next, the operation waits until the timer T3 reaches a predeterminedvalue t3 (Step S836). If it is judged that the timer T3 reaches thepredetermined value t3 and the lens arrives at the lower limit (StepS836: YES), the operation of the timer T3 is finished (Step S837). Acontent of the timer T2 is judged (Step S838) in order to discriminatethe loaded disk as the multiple-layer disk or the one-layer disk.

As mentioned above, in a case of the one-layer disk, the content of thetimer T2 is already cleared. Thus, it is possible, by judging whether ornot the content of the timer T2 exceeds 0 (Step S838), to discriminateit as the one-layer or multiple-layer. Namely, if the content of thetimer T2 exceeds 0 (Step S838: YES), the loaded disk is discriminated asthe multiple-layer DVD, similarly to the seventh embodiment. Theinterval between the layers is determined from the aforementionedjudgment expressions (1) and (2) on the basis of the value of the timerT2, similarly to the seventh embodiment (Step S839). At least one valueamong the pulse width, the peak value, the brake time and the gain uptime for the optimal focus jump is selected from the table, on the basisof the interval between the layers. Then, it is stored in the RAM 113(Step S840).

On the other hand, if the content of the timer T2 is 0 (Step S838: NO),the loaded disk is discriminated as the one-layer disk. Since it isnecessary to discriminate the loaded disk as the DVD or the CD, it isjudged whether or not the value of the timer T4 is equal to or more thana predetermined value t4 (Step S841). This predetermined value t4 is setto a middle value between the peak value interval in the case of the DVDand the peak value interval in the case of the CD, as shown in FIG. 23.If it is equal to or more than the predetermined value t4, the loadeddisk can be discriminated as the DVD. If it is less than the t4, theloaded disk can be discriminated as the CD.

Therefore, if it is more than the t4 (Step S841: NO), the loaded disk isdiscriminated as the DVD, and 2 is set to the register D (Step S842).Further, a focus gain, a tracking gain and an equalizer for the DVD areset (Step S843). On the other hand, if it is equal to or less than thet4 (Step S841: YES), the loaded disk is discriminated as the CD, and 1is set to the register D (Step S844). Further, a focus gain, a trackinggain and an equalizer for the CD are set (Step S845).

Since all of the disk discriminations are finished, the objective lensis again moved up (Step S846) in order to make the focus servo close.Then, a number that the peak value exceeds a threshold TH2 is counted tothereby judge the detected light as the 0 order light or the +1 orderlight. In case of the DVD, the focus is locked by the 0 order light. Incase of the CD, the focus is locked by the +1 order light. Namely, bysetting this threshold TH2 to a value smaller than the peak value of thefocus error signal for the +1 order light of the DVD, as shown in FIG.23, in a case of the one-layer DVD, the focus is made close when thepeak value of the focus error signal by the 0 order light exceeds thethreshold TH2 at a third time. In a case of the multiple-layer DVD, thefocus is made close when it exceeds the threshold TH2 at a fifth time.Or, in a case of the CD, the focus is made close when it exceeds thethreshold TH2 at a first time,.

Then, it is judged whether or not the value of the register D is 0 (StepS847) in order to initialize and set the values of the registers and thecounters, immediately after the objective lens is moved up. If the D is0 (Step S847: YES), an input to the register D is not performed, andthereby the loaded disk can be discriminated as the multiple-layer disk.Thus, a value of the counter E is set to 0, and a value of the registerb is set to 5 (Step S848). On the other hand, if the register D is not 0(Step S847: NO), the loaded disk can be discriminated as the one-layerDVD or the CD, as mentioned above. Therefore, the value of the counter Eis set to 0, and the value of the register b is set 3 (Step S849).

Then, it is judged whether or not the peak value exceeds the thresholdTH2 (Step S850). If it exceeds the threshold TH2 (Step S850: YES), thecounter E is incremented (Step S851). Next, the register D is judged(Step S852). Namely, if the register D is 1 (YES), the loaded disk isdiscriminated as the CD. Thus, in order to make the focus servo closewhen the focus error signal for the +1 order light is generated, thiscount process by the counter E is withdrawn (Step S852: YES). However,if the register D is 0 or 2, the loaded disk is discriminated as theDVD. Then, it is necessary to make the focus close when the focus errorsignal for the 0 order light is generated. Thus, the counting action ofthe counter E is repeated until the value of the counter E becomes thevalue of the register b set as mentioned above (Step S852: NO, and StepS853; NO).

After it is judged that the peak value of the focus error signal for the+1 order light or the 0 order light exceeds the threshold TH2 asmentioned above, the focus servo is made close (Step S854), and thetracking servo is made close (Step S855). Then, the reproduction isstarted (Step S856). If a stop command is issued (Step S857: YES), thereproduction is finished.

As mentioned above, parameters such as the pulse width of the kick pulseto jump the objective lens and the like are stored for themultiple-layer DVD. Thus, unless the disk is replaced after that, it ispossible to jump the objective lens based on the stored parameters tothereby jump to a position corresponding to each of the informationrecord layers accurately and quickly. Moreover, it is possible toperform the discrimination for the multiple-layer DVD, the one-layer DVDand the CD to thereby perform the correct focus servo control.

[XII] Ninth Embodiment

Next, a ninth embodiment of the present invention is explained withreference to FIGS. 24 to 27. Incidentally, identical reference numbersare assigned to parts common to the seventh embodiment. Then, theexplanations thereof are omitted. This embodiment performs a focus gainadjustment and a tracking gain adjustment for each of the layers in themultiple-layer DVD, and simultaneously measures the interval between thelayers.

FIG. 24 shows a block diagram indicating a schematic structure of theservo circuit 110 of the reproducing apparatus shown in FIG. 16. Theother configuration of the reproducing apparatus of this embodiment isthe same as the apparatus shown in FIG. 16. As shown in FIG. 24, an LPF(Low Pass Filter) 120 removes unnecessary frequency components equal toor more than a sampling frequency of an A/D converter 122 describedlater, from the focus error signal FE.

An amplifier 121 amplifies the focus error signal FE up to apredetermined voltage value to output it, and also changes the amplifiedamount on the basis of a focus servo gain from an FGA 123 describedlater.

The A/D converter 122 converts the focus error signal FE amplified bythe amplifier 121 into a digital signal, outputs it to the next FGA 123and also outputs this digitized focus error signal FE to a servocontroller 132 described later.

The FGA 123 applies feedback to the amplifier 121 on the basis of thefocus error signal FE outputted by the A/D converter 122, andautomatically adjusts a focus servo loop gain.

A digital equalizer circuit (D-EQ) 124 is composed of a digital filterand the like, and sets a focus servo frequency band corresponding to thefocus error signal FE converted into the digital signal, on the basis ofa control signal from the servo controller 132 described later.

A PWM (Pulse Width Modulation) circuit 125 generates a focus drivesignal FD having a pulse width corresponding to a signal level from thedigital equalizer circuit 124.

An LPF 126, an amplifier 127, an A/D converter 128, a TGA 129, a digitalequalizer circuit 130 and a PWM 131 are equipped in order to generate atracking drive signal TD from a tracking error signal TE, similarly tothe focus servo loop. Then, operations are performed which correspond tothe respective means constituting the focus servo loop.

Further, a TRBL 133 is equipped which performs an automatic control of atracking balance, on the basis of the control signal from the servocontroller 132, in order to adjust the tracking balance. This TRBL 33feeds back to the RF Amplifier 103 a TBC signal of adjusting a centerlevel of the tracking error signal.

The servo controller 132 as one example of a servo calculation deviceand a servo controlling device calculates, on the basis of the focuserror signals as described later, peak values thereof, and furtheroutputs a control signal of setting a focus servo gain from an averageof the peak values, and a control signal of setting a focus servofrequency band. Moreover, it calculates, on the basis of the trackingerror signals, peak values thereof, and further outputs a control signalof setting a tracking servo gain from an average of the peak values, anda control signal of setting a tracking servo frequency band.Incidentally, data required to perform the focus servo control and thetracking servo control and the like are stored in a RAM 135 as oneexample of a gain memory.

A setup operation of the reproducing apparatus of this embodiment isexplained which comprises the servo circuit 110 having the abovementioned structure. As shown in FIG. 25, it is firstly judged whetheror not the disk is set (Step S860). If the disk is judged to be set(YES), the CPU 109 performs the initializing actions (Step S861). Thatis, it clears the content of the RAM 113 and clears registers includedin the CPU 109, for example, a counter N and a counter M describedlater, and a timer of the servo controller 32 and the like.

Next, the disk discrimination is performed (Step S862). In this diskdiscrimination process, the objective lens is firstly moved to a lowerlimit as shown in FIG. 27 (Step S62-1).

In FIG. 27, next, while the objective lens is moved up (Step S62-2), itis judged whether or not the peak value of the focus error signalexceeds the threshold TH3 (Step S62-3). This threshold TH3 is set to avalue smaller than the peak value of the focus error signal for the 0order light in a case of the CD, as shown in FIG. 28A. In order togenerate a focus error signal shown in FIG. 28A, a light division ratioof the 0 order light to the +1 order light in the optical pickup 2 isset to, for example, 70% to 30%, in this embodiment. When setting asmentioned above, a large focus error signal can be obtained for the 0order light, even if the disk is the CD or the DVD. However, the focuserror signal in a case of the DVD is larger than that in a case of theCD. Thus, even if the peak value of the obtained focus error signalexceeds the threshold TH3, when it is less than the threshold TH1, thedisk can be discriminated as the CD. When it exceeds the threshold TH1,the disk can be discriminated as the DVD.

If the peak value of the focus error signal exceeds the threshold TH3(Step S62-3: YES), it is judged whether or not the peak value furtherexceeds the threshold TH1 (Step S62-4). If it does not exceed (StepS62-4: NO), the disk is discriminated as the CD, and 1 is set to theregister D (Step S62-5). On the other hand, if it exceeds the thresholdTH1 (Step S62-4: YES), the operation of the timer T1 is started (StepS62-6) in order to judge whether or not the DVD has the multiple layers.Then, it is judged whether or not the value of the timer T1 reaches thepredetermined value t1 and the objective lens arrives at the upper limit(Step S62-7). Moreover, it is judged whether or not a focus error signalexceeding the threshold TH1 is generated again before the value of thetimer T1 reaches the predetermined value t1 (Step S62-8). In a case ofthe two-layer disk of the DVD, it is possible to obtain the focus errorsignal exceeding the threshold TH1 before the objective lens arrives atthe upper limit as shown in FIG. 28A (Step S62-8: YES). Thus, the diskis discriminated as the two-layer disk, and 3 is set to the register D(Step S62-9). On the other hand, when it is impossible to obtain thefocus error signal exceeding the threshold TH1 before the timer T1reaches the predetermined value t1 (Step S62-7: YES), the disk isdiscriminated as the one-layer DVD, and 2 is set to the register D (StepS62-10).

As mentioned above, after any of the values is set to the register D,the operation of the timer T1 is finished (Step S62-11). The up actionof the objective lens is finished (Step S62-12). The objective lens ismoved down to the lower limit (Step S62-13). The disk discriminationprocess is finished.

In this embodiment, the following process is performed only in a case ofthe two-layer DVD. This reason is that, since the focus gain values andthe tracking values in the first and second layers are different fromeach other in case of the two layer DVD, it is intended to store thefocus gain value and the tracking gain value for each layer to therebyperform the proper focus servo and tracking servo.

Therefore, in order to check the discriminated result in the diskdiscrimination process, it is judged whether or not the value of theregister D is 3 as shown in FIG. 25 (Step S863).

In FIG. 25 again, if the register D is not 3 (step S863: NO), and thedisk is discriminated as the one-layer DVD or the CD, the servo closeprocess is performed similarly to the eighth embodiment (on and afterthe step S846 in FIG. 22). Incidentally, the processes this point areperformed by the CPU 109, and processes on and after this point areperformed by the servo controller 132, except a particular process.

On the other hand, If the value of the register D is 31 (step 863: YES)and the disk is discriminated as the two-layer DVD, the counter N forcounting the number of the up and down actions of the objective lens isincremented, and the counter M for counting the focus error signals isincremented (Step S864).

Then, while the objective lens is moved up (Step S865), it is judgedwhether or not the focus error signal exceeding the threshold TH1 isdetected during the up action of the lens (Step S866). The focus errorsignal exceeding this threshold TH1 is only the signal for the 0 orderlight. Only the focus error signal for the 0 order light is illustratedafter the disk discrimination in FIG. 28A. For an easy explanation, theinterval between the focus error signals after the disk discriminationprocess is widely illustrated in FIG. 28A.

In FIG. 25 again, if the focus error signal exceeding the threshold TH1is detected (Step S866: YES), timers T5, T10 are actuated (Step S867).

This timer T5 is used to determine a timing of counting one focus errorsignal. The timer T10 is used to measure the interval between the layersin a case that the loaded disk is the multiple-layer DVD, similarly tothe seventh embodiment.

Next, a peak to peak value FEpp (M) of the focus error signal is takenin and stored (Step S868). This peak to peak value FEpp (M) is used tolater adjust the focus gain.

After that, the operation waits until the timer T5 exceeds apredetermined value t5 (Step S869). If it exceeds, the timer T5 isfinished (Step S870). It is judged that an output of one focus errorsignal is finished. Then, the counter M is incremented (Step S871).

Next, it is judged whether or not the focus error signal exceeding thethreshold TH1 is detected from the focus error signals for the secondlayer (Step S872). If such a focus error signal is detected (Step S872:YES), an operation of a timer T6 is started (Step S873) in order tomeasure an interval up to the upper limit of the objective lens.Further, the operation of the timer T10 for measuring the intervalbetween the layers is finished (Step S874).

Then, a peak to peak value FEpp (M) of the focus error signal in thissecond layer is taken in and stored (Step S875). After that, theoperation waits until the timer T6 reaches a predetermined value t6 andthe objective lens arrives at the upper limit (Step S876). After that,if it is judged that this timer T6 reaches the predetermined value t6and the objective lens arrives at the upper limit (Step S876: YES), thetimer T6 is finished (Step S877).

In the process to this point, the objective lens is positioned at theupper limit, as shown in FIG. 28A. The counter N for counting the up anddown actions of the objective lens is 1. Bifocal error signals aredetected during this period. Thus, the counter M of the focus errorsignal is 2. Moreover, the peak to peak values for the respective focuserror signals are stored.

Next, the objective lens is moved down (Step S878). The counters N and Mare incremented (Step S879). Then, it is judged whether or not the focuserror signal exceeding the threshold TH1 is detected from the focuserror signals for the second layer in the down action (Step S880). Ifthe focus error signal exceeding the threshold TH1 is detected (StepS880: YES), an operation of a timer T7 for determining a timing ofmasking the focus error signal is started (Step S881). The peak to peakvalue FEpp (M) of the focus error signal is taken in and stored (StepS882).

After that, the operation waits until the timer T7 exceeds apredetermined value t7 (Step S883). If it exceeds, the timer T7 isfinished (Step S884). It is judged that an output of one focus errorsignal is finished. Then, the counter M is incremented (Step S885).

Next, it is judged whether or not the focus error signal exceeding thethreshold TH1 is detected from the focus error signals for the firstlayer (Step S886). If such a focus error signal is detected (Step S886:YES), an operation of a timer T8 is started (Step S887) in order tomeasure an interval down to the lower limit of the objective lens.

Then, a peak to peak value FEpp (M) of the focus error signal in thisfirst layer is taken in and stored (Step S888). After that, theoperation waits until the timer T8 reaches a predetermined value t8 andthe objective lens arrives at the lower limit (Step S889). If the valueof the timer T8 reaches the predetermined value t8 (Step S889: YES), thetimer T8 is finished (Step S890).

In the process to this point, the objective lens is positioned at thelower limit, as shown in FIG. 28A. The counter N for counting the up anddown actions of the lens is 2. Bifocal error signals are detected duringthis period. Thus, the counter M of the focus error signals is 4.Moreover, the peak to peak values for the respective focus error signalsare also stored.

After that, the above mentioned process is repeated until the counter Nbecomes 4 (Step S891: NO, through Step S864). The process is stopped ata time point when the counter N becomes 4 (Step S891: YES). Thus, peakto peak values of four focus error signals are obtained respectively forthe first layer and the second layer, at this time point.

Then, the focus gain value is calculated by calculating an average ofthe peak to peak values of the four focus error signals for each layer.Accordingly, the focus gain is adjusted (Step S892). Further, the focusgain values of the first and second layers are stored in the RAM 35.

Next, the CPU 109 determines the interval between the layers similarlyto the seventh embodiment (Step S894) on the basis of the previouslymeasured value of the timer T10, and selects at least one value amongthe pulse width, the peak value, the brake time and the gain up time forthe optimal focus jump from the table, on the basis of the intervalbetween the layers, and stores in the RAM 113 (Step S895).

In FIG. 26, then, the servo controller 132 moves up the objective lens(Step S896), and makes the focus servo in the first layer close, on thebasis of the above calculated focus gain value in the first layer (StepS897). Next, an operation of a timer T12 is started (Step S898) in orderto adjust the tracking balance in the first layer. A process of takingin a center level of the tracking error signal TE (Step S899) as shownin FIG. 28B is continued until a value of the timer T12 reaches apredetermined value t12 (Step S900: NO). If the value of the timer T12reaches the predetermined value t12 (Step S900: YES), the operation ofthe timer T12 is finished (Step S901). The tracking balance in the firstlayer is adjusted (Step S902) on the basis of the value of the centerlevel of the tracking error signal TE taken in the above manner.

A timer T13 is actuated (Step S903) in order to adjust the tracking gainin the first layer. A process of taking in a peak to peak value TEpp ofthe tracking error signal TE (Step S904) as shown in FIG. 28B iscontinued until a value of the timer T13 reaches a predetermined valuet13 (Step S905: NO). If the value of the timer T13 reaches thepredetermined value t13 (Step S905: YES), the timer T13 is stopped (StepS906). The tracking gain in the first layer is adjusted (Step S907) onthe basis of the value of the peak to peak value TEpp of the trackingerror signal TE taken in the above manner. The tracking servo is madeclose (Step S908). The tracking gain value in the first layer is storedin the RAM 135 (Step S909).

Next, in order to perform the above similar process for the secondlayer, the lens is jumped to a position relative to the second layer(Step S910), on the basis of the pulse width, the peak value, the braketime, the gain up time and the like for the previously stored kickpulse. The focus servo of the second layer is made close (Step S911) onthe basis of the above calculated focus gain value for the second layer.Next, an operation of a timer T14 is started (Step S912) in order toadjust the tracking balance for the second layer. A process of taking ina center level of the tracking error signal TE (Step S913) as shown inFIG. 28C is continued until a value of the timer T14 reaches apredetermined value t14 (Step S914: NO). If the value of the timer T14reaches the predetermined value tl4 (Step S914: YES), the operation ofthe timer T14 is finished (Step S915). The tracking balance in thesecond layer is adjusted (Step S916) on the basis of a value of thecenter level of the tracking error signal TE taken in the above manner.

An operation of a timer T15 is started (Step S917) in order to adjustthe tracking gain for the second layer. A process of taking in a peak topeak value TEpp of the tracking error signal TE (Step S918) as shown inFIG. 28C is continued until a value of the timer T15 reaches apredetermined value t15 (Step S919: NO). If the value of the timer T15reaches the predetermined value t15 (Step S919: YES), the operation ofthe timer T15 is finished (Step S920). The tracking gain for the secondlayer is adjusted (Step S921) on the basis of a value of the peak topeak value TEpp of the tracking error signal TE taken in the abovemanner. The tracking servo is made close (Step S922). The tracking gainvalue for the second layer is stored in the RAM 135 (Step S923).

It is possible to perform the above mentioned processes to therebyperform the focus servo control and the tracking servo that areappropriate and accurate for each of the layers, and also possible tomeasure the interval between the two layers in the single layer tothereby set the optimally jumping condition. As a result, it is possibleto jump between the layers accurately and quickly.

In the above mentioned examples, the present invention is applied to theapparatus which can reproduce both the CD and the DVD. However, thepresent invention is not limited to the examples. The apparatusdedicated to the DVD reproduction is allowable. Thus, it is notnecessary that the optical pickup uses the above mentioned bifocal lens.It is allowable to use an optical pickup comprising a single-focus lens.Or, a type of switching between the respective lens for the CD and theDVD can be used similarly.

As for a moving direction of the lens at a time of measuring theinterval between the layers, the example in which it is started from theup direction is explained. However, the present invention is not limitedto the example. It is allowable to be started from the down direction.

In this embodiment, the pulse width, the peak value, the brake time andthe gain up time for the focus jump are all selected, and all stored inthe RAM. However, the present invention is not limited to it. It isallowable to select and store any one value or several values of them.

In this embodiment, the focus error signal resulting from the 0 orderlight is used to determine the interval between the layers in each ofthe record layers. However, it is possible to use the focus error signalresulting from the +1 order light or the pseudo light. At that time, aninterval between the focus error signals is determined by properlychanging a threshold.

In a case of a disk in which both surfaces of two layers are bondedtogether, it is possible to perform the various adjustments similar tothis embodiment for two layers on an upper side and two layers on alower side at a time of a first setup, to thereby record with layerinformation in the respective layers. Moreover, it is naturally possibleto store and use a plurality of respective adjustment values with theinformation peculiar to the disk.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof.

The present embodiments are therefore to be considered in all respectsas illustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

What is claimed is:
 1. In an information reproducing apparatus forreproducing information from a multiple layer disk, a method ofpreparing for reproducing the information from the multiple layer disk,the multiple layer disk comprising a plurality of layers including atleast a first layer and a second layer, the information being recordedon each of the first layer and the second layer, the informationreproducing apparatus comprising: a light emitting device that emits alight beam to the first layer or the second layer; an objective lensthat focuses the light beam on the first layer or the second layer; afocus servo device that carries out a focus servo control forcontrolling a focal position of the light beam with respect to the firstlayer or the second layer; a tracking servo device that carries out atracking servo control for controlling a position of the light beam in aradial direction of the multiple layer disk with respect to the firstlayer or the second layer; a reproducing device that reads theinformation recorded on the first layer or the second layer using thelight beam and that reproduces the read information under the focusservo control and the tracking servo control; a memory device thatstores various values, the method comprising the processes of:determining a first gain value to be used for the focus servo controlwith respect to the first layer, by detecting a focus error signal withrespect to the first layer; determining a second gain value to be usedfor the tracking servo control with respect to the first layer, bydetecting a tracking error signal with respect to the first layer;determining a third gain value to be used for the focus servo controlwith respect to the second layer, by detecting a focus error signal withrespect to the second layer; determining a fourth gain value to be usedfor the tracking servo control with respect to the second layer, bymultiplying the second gain value by a ratio of the third gain value tothe first gain value; and storing the first through fourth gain valuesinto the memory device, wherein the processes of determining the firstthrough fourth gain values and the process of storing the first throughfourth gain values are carried out before a start of reproducing theinformation from the multiple layer disk.
 2. In an informationreproducing apparatus for reproducing information a multiple layer disk,a method of preparing for reproducing the information from the multiplelayer disk, the multiple layer disk comprising a plurality of layersincluding at least a first layer and a second layer, the informationbeing recorded on each of the first layer and the second layer, theinformation reproducing apparatus comprising: a light emitting devicethat emits a light beam to the first layer or the second layer; anobjective lens that focuses the light beam on the first layer or thesecond layer; a focus servo device that carries out a focus servocontrol for controlling a focal position of the light beam with respectto the first layer or the second layer; a tracking servo device thatcarries out a tracking servo control for controlling a position of thelight beam in a radial direction of the multiple layer disk with respectto the first layer or the second layer; a reproducing device that readsthe information recorded on the first layer or the second layer usingthe light beam and that reproduces the read information under the focusservo control and the tracking servo control; a memory device thatstores various values, the method comprising the processes of:determining a first gain value to be used for the focus servo controlwith respect to the first layer, by detecting a focus error signal withrespect to the first layer; determining a second gain value to be usedfor the tracking servo control with respect to the first layer, bydetecting a tracking error signal with respect to the first layer;determining a third gain value of an RF signal with respect to the firstlayer; determining a fourth gain value to be used for the focus servocontrol with respect to the second layer, by detecting a focus errorsignal with respect to the second layer; determining a fifth gain valueto be used for the tracking servo control with respect to the secondlayer, by detecting a tracking error signal with respect to the secondlayer; determining a sixth gain value of an RF signal with respect tothe second layer; and storing the first through sixth gain values intothe memory device, wherein the processes of determining the firstthrough sixth gain values and the process of storing the first throughsixth gain values are carried out before a start of reproducing theinformation from the multiple layer disk.
 3. In an informationreproducing apparatus for reproducing information from a multiple layerdisk, a method of preparing for reproducing the information from themultiple layer disk, the multiple layer disk comprising a plurality oflayers including at least a first layer and a second layer, theinformation being recorded on each of the first layer and the secondlayer the information reproducing apparatus comprising: a light emittingdevice that emits a light beam to the first layer or the second layer;an objective lens that focuses the light beam on the first layer or thesecond layer; a focus servo device that carries out a focus servocontrol for controlling a focal position of the light beam with respectto the first layer or the second layer; a tracking servo device thatcarries out a tracking servo control for controlling a position of thelight beam in a radial direction of the multiple layer disk with respectto the first layer or the second layer; a reproducing device that readsthe information recorded on the first layer or the second layer usingthe light beam and that reproduces the read information under the focusservo control and the tracking servo control; a memory device thatstores various values, the method comprising the processes of:determining a first equalizer value to be used for the focus servocontrol with respect to the first layer, by detecting a focus errorsignal with respect to the first layer; determining a second equalizervalue to be used for the tracking servo control with respect to thefirst layer, by detecting a tracking error signal with respect to thefirst layer; determining a third equalizer value to be used for thefocus servo control with respect to the second layer, by detecting afocus error signal with respect to the second layer; determining afourth equalizer value to be used for the tracking servo control withrespect to the second layer, by multiplying the second equalizer valueby a ratio of the third equalizer value to the first equalizer value;and storing the first through fourth equalizer values into the memorydevice, wherein the processes of determining the first through fourthequalizer values and the process of storing the first through fourthequalizer values are carried out before a start of reproducing theinformation from the multiple layer disk.